What Is Brink Exactly About And What Are Its Characteristics.?

I want to know what is BRINK exacly about before i buy it. Is BRINK a campaign or ,multiplayer game. I think its like a multiplayer experinece were you earn xp mixed with a storyline. Does this game have an actual storyline or its just multiplayer matches. What do you use your xp for, What are the attachments available for weapons, are the weapons real weapons are they are weapons from the own game????? Is there anything like a challenge mode so if you get bored you get to build up some xp in a different fun way. Is the game a 1st person shooter or 3rd person, or you can switch between. Also, lets say i dont have xbox live, i guess ill be playing with computer bots, is the AI of these bots smart or these enemies are just going to act retarded once they see you. I heard about different types of things like, The option were you are heavy and hard to kill or your light, fast, but easier to kill and something called engeneer???? Explain everything you can,,, thank you