I've seen advertisements for Ultimate Team, but never got a good grasp of what it is. What does it actually add to the game?
Additionally, I've seen it on the Playstation Store available for free. Is this correct, or does it have a cost?
Ultimate Team is a Collectible Card Game applied to FIFA. You buy packs of (virtual) cards which represent players, staff, and items such as different balls and powerups. You use your cards to put together a team, and then you play other people online using that team. Playing matches earns you Coins, which you can use to buy new card packs, or buy individual cards from other players.
Playing a match is similar to a normal FIFA match, except you can use powerup items which grant abilities such as "lenient referee".
The initial download is free, and you will not need to pay anything to start playing, but you have the option to buy additional card packs for real money rather than using Coins.