I am surprised why Gamespot did not gave this amazing game a good profile page. This game rocks
In order to unlock all these you must have money (PEN). You earn then if you play in games ( the best player wins more points) or by doing missions.
You can also change you character's appearance by buying clothes. You can just buy the cloth just for fun or if you pay more you can add other such as 10% more experience.
There are two game types; Deathmatch (DM) and TouchDown (TD). At DM, the team (up to 6 players each) must have more kill points (the sum of each player's kill) than the enemy team. At TD, each team has a command post and a player must get a ball and put it to the enemy's command post. It is difficult and it requires teamwork.
To conclude, S4 is an amazing game which combines both weapons and MMO. Every shooter fan must download it. You can just try it and if you don't like it just remove it.