What are Pivots for?

So I've completed the game now and am at 99% Animus DB complete. I did the two Epilogue missions and then got a mission icon in Boston. I zoned into Boston and the game loaded, then immediately went back to the loading screen. After it had loaded I was in what appeared to be the middle of a conversation with a character I don't recognise who was talking about Pivots.

They neglected to tell me who they were, what the pivots were for or anything. Then after that I had a bunch of message coming up telling me that the 'Weather change hack unlocked' along with something like 'Man of steel hack'.

Now I have these glowing horse things which I can place on the map, but I've no idea what they are, what they are for or how they work. To add to this when looking at the Pivot part in the map there seems to be a timer on this which is counting down continually.

Does anyone know what my objective is with the part of the game please?

Pivots give you animus hacks - think of them as cheats.

How it Works:
As stated earlier, Pivots only become available after finishing the game once or in the epilogue after you complete the campaign.

You can only find Pivots while you are online; there is a reason for that. However, the initial tutorial, which aids you in finding three basic pivots, can be carried out offline. The rest of the pivots must be unlocked online.

This is because the rest of the pivots are actually placed by other online players who are also busy in the same purpose. To find these pivots, you would need to triangulate the position of these player-placed pivots with the ones you have already found.

This may sound confusing, but the idea develops rapidly after trying out the tutorial. Basically, placing two pivots will create a sort of border or hemisphere on the map. The green portion of the cut map will be the place where a pivot may be present.

To narrow it down, you must have another pivot placed to create a triangular green zone, which should have a pivot at the average center of that triangle. The pivot is designated with a square icon on your mini-map.

You can place found pivots on the map for triangulated other pivots through your map screen. However, you can only place pivots at the position where Connor is standing.

This means that in order to create a triangle, you would actually have to travel to the desired edges of the triangle that you want to create to place each pivot there. However, this does not apply to the removing of pivots. Placed pivots can be removed simply by hovering the cursor of them.

Pivots aren’t present all the time though – there is a spawn time limit for every pivot. Pivots will spawn on the map after every 15 minutes.

Since pivots you find are placed by other players online, you are actually involved in the same procedure. This means that other players can find the pivots you place for searching other pivots. When a player finds your pivot, its position will change on the mini-map.

The Cheat List:
Finding pivots will unlock 10 different cheats. This means that you are required to find 10 different pivots. Once a pivot is collected, you can use the cheats through the options menu.

Here are the cheats along with their function:

Made of Steel – Invincibility
Infinite Ammunition – Infinite ammunition for pistols and bow
Season Changer – Player can switch seasons between summer and winter
Weather Man – Change the weather conditions
Thunder Kill – Thunder and lightning follows every kill in the game
Sun and Moon – Player can switch between day or night
Semi-Automatic – Ranged weapons have no reload time between each shot
Killing Spree – Enemies can be assassinated even while player is not in stealth
Recruit – Obtain infinite recruit tokens
Ninja – Enemies completely ignore you no matter what

Source: http://segmentnext.com/2012/11/01/assassins-creed-3-pivot-points-locations-to-unlock-animus-hacks-cheats/