User blog comment:Peteparker/Help! Assassin's Creed III, I don't get it./@comment-5579230-20121106230800

If you cant understand the history but dont want to bother buying the other games, then you should see some videos on Youtube or articles on this Wikia.

Side missions are in fact, a lot, you can do them in any time and in any order.

Main Missions are that black exclamation thing on the map, you can just keep doing it and you will complete the game. If you are playing with Desmond, you either go to the Animus (that red chair that you sit on to play) or just pay attention to what the game "tells" you to do, including story dialogue.