What does it mean 'All mid all random' in League Of Legends?

Solution 1:

All players should pick a random hero, and everyone should only go into the middle lane.

Solution 2:

ARAM games are custom games set to the "all random" mode. Your champion is picked for you from the pool of champions you own + champions that are free this week. ARAMs also have some player-enforced rules:

1. You cannot leave mid lane. Do not enter the bushes or the jungle.
2. You cannot travel back to your base to heal unless your mid lane inhibitor is down.
3. You cannot use Recall.
4. You cannot buy items from the shop until you die (because of #2 and #3).
5. You cannot buy Guardian Angel.
6. You cannot buy "snowball" items that stack on player kills: Mejiai's Soulstealer, Sword of the Occult, and Leviathan.

There are also some rules that aren't always enforced but you'll commonly see:

1. The summoner skill Fortify is also banned.
2. You have to give the other team a free kill on you if you break a rule. And you have to sell a banned item if you buy it.