Are different champions required for different lanes?

I have been playing League of Legends for some time now, and I'm still trying to understand the positions. Do top, mid, and bot require different champions, or can they all be played with whatever champion you choose?

Summarized we can say that the reason for splitting the team on several lanes is the attempt to gain the maximum amount of experience and gold.

Since there are only 4 lanes (if Jungle is seen as a "lane") but 5 Champions per team we get to the first role, the Support:

Supports make plays by enabling their allies through buffs and heals, or by disrupting enemy lines through crowd control. From laning to late game teamfights, supports create advantages and opportunities for their teammates to capitalize on. A skilled support gives their team the edge it needs to claim victory, and can turn the tide of battle with just one well-timed play.

Warding (Placing wards to grant sight for the entire team) also became a high-prior task for the support.

A typical support champion is a champ with abilities which don't require a high amount of AP or AD to become useful (e.g. Stuns, Heals, Slows) and so the support is able to buy wards and supporting items. Due to this fact the support doesn't farm minions or take champions kills (unless he is alone in a certain situation) and so he shares a lane with the probably most vulnerable champion in a common match-up, the ADC:

ADC, aka Attack Damage Carry, is an archaic term used to refer to a champion that deals strong, continuous damage with their basic attacks and scales with attack-related stats - i.e. attack damage, critical strike chance and attack speed.

A typical ADC needs to be high-itemized to become strong and so he needs as much gold as possible to get those items. Since he is vulnerable for ganks the support tries to gain sight and so deny ganks from the opponent Jungler:

Junglers rely on killing neutral monsters in the jungle to keep up with their laning teammates in terms of gold and experience. In a standard 5-on-5 game of League of Legends, 4 players on a team will be Laners, and 1 player will be a designated Jungler.

The extract from above starts out from the best case, namely that your lanes do very well and noone needs the Jungler's help and so he tries to not fall behind by farming the neutral monster camps. In the jungle there can possibly be any champ but there are criterias which make a champ to a possible good jungler:

• High sustain: While champions on the the lane usually try to deny getting attacked by minions a jungler is always attacked during farming the monster camps and so high sustain means more gold due to less backports to base.
• High ganking potential: Champions with gap-closers (Skills which allow to cross huge distances in a fairly small time) and/or CC (Crowd Control) fall into this categoria.
• High counterjungling potential: A counter-jungler tries to keep the opponent jungler weak by stealing his camps. It's often a combination of the two other criterias, since there should be e.g. gap closers to escape out of the opponent jungle being in danger but also there should be high sustain in order that you don't have to move with low HP in the enemy jungle and so getting killed easily.

In the top-lane there is a tank in the current meta:

Tanks are tough melee champions who sacrifice damage in exchange for powerful crowd control. While able to engage enemies in combat, a tank's purpose isn't usually to kill opponents; rather, tanks excel at disrupting enemies and diverting their focus to themselves, allowing them to lock down specific targets (or several targets at once), as well as remove (or peel) threats from their allies. In addition to strong base defenses, tanks generally have a means of amplifying their tankiness even further with their abilities, and tend to fully invest in defensive items to maximize their resilience. However, tanks lack the tools to truly succeed in single combat, and their influence is limited by their low overall mobility, preventing them from constantly staying on top of their targets. As tanks can handle burst damage very well, they tend to succeed against assassins and mages, but their vulnerability to continuous damage puts them at a disadvantage against fighters and marksmen.

While tank mostly refers to builds without any offensive items there are also others terms for top laners like fighter or duelist. Such an offensive tank can also deal high amounts of damage but is likely not able to hard engage in the enemy team without any contemplations. Deep diving into enemy towers also belongs into this section.

Most top-laners pick teleport as summoner spell in order to get quickly onto other lanes for helping or getting back to lane e.g. after a gank asap. The common way for supporting other lanes as top laner is to push the lane to the opponent tower and trying to get back before the enemy top laner is pushing your tower. In this regard communication with the jungler can be impotant as well.

Now there is only one lane missing and so far we have probably mainly physical damage (unless there is a high magic damage jungler or top-laner) and so the common match-up involves an AP mid-laner (mage):

Mages are mostly ranged champions who prioritize powerful abilities over basic attacks. Typically mages are characterized by some combination of long-range, area-effect or high-utility spells to get the job done. A skilled mage can have a huge impact on any team with their versatile skillsets and flexible playstyle.

Due to its central lane the mid-laner is able to help bot, top and jungle. There are also assasins played in mid lane that are able to turn off important squishy targets (ADC or Mid) quickly and with high probability. The "normal" mage has usually high AoE-Damage so that the enemies become low, giving easy-killable targets for e.g. your ADC.

Note: Exceptions to the rule.

Examples: Tryndamere top, Mordekaiser bot, Yasuo mid, to give just a small list.

This question depends a lot on the current state of the game, also called meta.

As a standard there is a tank top a mage/assasin mid ad and support bot and a jungler.

You want to choose a champion that fits the role you are playing at least for now until you have aquired more game knowledge.

The thing about lanes is that everyone is used to those and it would require a different playstyle to successfully pull off other team compositions which doesnt happen too much in games because the communication is lacking compared to "real" teams that talk over skype or ts.

• Top

Top laners are generally the tanks. A prime example would be Mundo or Malphite. Their skills provide tankieness and high base damages with little scaling, so putting much gold into damage is less effective than just building tank stats. They have a solo lanes to aquire as much gold and levels as possible to be tanky and get their base dmg up.

• Mid

Mid laners are highly scaling with items and try to burst enemies down quickly. Much like toplaners they need a lot of gold and exp.

• ADC

ADCs Are ranged and scale with attack dmg. Mostly that have some skills that enhance their auto-attack damage. Unlike the bust mages in mid they do continious damage. An example here is Vayne, her Tumble does 50%bonus damage and she deals true damage every 3rd hit. ADCs are very dependend on gold but not so much on exp.

• Supports

They are as their names say there to support their ADCs by providing untility based spells (heals, shields, stuns, ...) they dont scale well with items so they dont need a lot of gold or exp so they share a lane with the ADC. Soraka her for heals, heals and more heals.

• Junglers

They need to survive in the jungle obviously, they should be able to gang well, be able to tank a bit, do some damage and provide some utility. Basically they are all-rounders that dont excel at anything. Their strength lies in the early and mid game when the other lanes havent build up their strengths yet.

Strictly speaking you can bring any character wherever you want, but the current meta developed for several good reasons, which means shaking it up should be done with a specific strategy in mind.

First, the reason an ADC + support lane is so popular is because ADCs are typically among the most fragile characters on a team. They're designed to be glass cannons, able to dish out lots of damage from a range where their opponents (hopefully) can't reach them, so their laning phase would be particularly difficult if they were alone and against a counter-pick, because there's very little "outplay" potential for characters who deal most of their damage through auto-attacks. (This is less true as of the recent updates which increased the variety in abilities available to marksmen, but it's still largely the case.)

So supports exist to help their ADCs survive through laning phase without needing to split gold. This usually means they provide crowd control (to push for kills or peel enemies away) or sustain (healing and shields). You can play without a support, but this means that two characters will be splitting their gold income from lane minions, and you'll largely be aiming to score kills on the enemy laners to gain an advantage. This is usually only a viable strategy at lower levels of play, since highly skilled players will know to simply farm safe under their turret and wait until they get ahead in items (or even wait until teams start converging on objectives) to fight.

You could even send other types of carries bot lane instead of an ADC, but the reason ADCs are so popular there is because they scale insanely well with items and become absolute monsters in the late-game. The fact that some marksmen have become popular in the mid lane makes this pick potentially more flexible, but most pros haven't shaken it up much.

The reason mid laners are often utility mages or assassins is because those characters can offer some of the best roaming and ganking potential. You could certainly play an ADC in the mid lane, but most characters played mid lane these days are specifically designed to destroy ADCs in one burst, or can outlast them in lane with poke damage. Corki and Varus have been played mid lately because of their ability to deal considerable damage safely from long range, but their mid lane builds are also very different from the ones they use as bot lane marksmen.

Top laners tend to be fighters and tanks for a couple of reasons. The first is that having a mix of melee and ranged characters allows the ADC and/or mid mages to stay behind a big, burly threat while dealing their damage. The second is related to the reason that having the ADC/support lane in bot is considered optimal: dragon control. Fighters and tanks tend to have some of the best gank potential due to their reasonable early/mid game damage and crowd control abilities, and top laners (especially in this last season) usually take teleport so they can help if their team wants to take dragon and things get messy. (They obviously can use teleport for other things such as just ganking, but dragon control is the reason it became immensely popular for top laners.) You can certainly try to take a ranged character top lane (Quinn top was popular for a while because she could shut down a lane pretty easily between her blind and her vault) but generally tanks and fighters will out-scale you in the mid-game and you won't have anybody to peel for you until your team starts grouping for fights.

Jungle is probably the most restrictive role simply because you need to be able to farm the jungle without dying. This requires that you pick a character who can either self-heal in the jungle or simply clear fast enough that it doesn't matter. The other restriction for junglers is usually their ability to gank; most teams have an expectation that a jungler will interact with the lanes, helping to snowball their lanes that get ahead and help losing lanes to catch up. This means just being able to deal damage isn't usually enough: you need some kind of crowd control abilities. For this reason tanks and fighters are the likeliest jungle picks, although Graves' abilities on the latest patch make jungling pretty easy for him, and Kindred was specifically designed to be a jungler marksman.

Overall, there are lots of options to choose from, but at lower levels people usually won't be able to respond to (or play around) off-meta picks, so they should be made with caution.