Ultimate team is the "main" mode on the game. You basically start off with bad players and have to play the game to unlock challenges, packs, to build your team up. Basically starting off with Cardiff City and you will eventually get to Barcelona quality players. Coins are used to purchase players off the transfer market that other real life users place on. They pack a player and don't want them, they can place them on a transfer market that all players on the specific console could purchase for in game coins. The in game points (FIFA Points) accelerate the process because you build your a lot quicker than the lay person due to the amount of players you get on your team. You are able to sell the people on the transfer market to get coins to eventually buy the higher quality players. Sorry for this word vomit but it sounded good in my head.