I am brand new to games like this. I finished what I am assuming is the only single player campaign. How do you know what level you are? Are there more campaigns for single player? How are players able to level? What is the difference at that level? Are you stronger? Are there more abilities to aquire?

You have 4 different difficulties in single player mode, no levels.

The levels everyone refers to, level 1 up to level 50, are in multiplayer mode. You start out as level 1, build xp (experience) points by playing against others and/or on teams and build your levels up.

There are several maps and types of games in multiplayer mode. Instant Action (every man for himself), team instant action (team vs. team), Capture the Relay (team v. team), Assault (not sure of this one, never played it) and a few others that I can't remember at the moment.

The higher the level and more xp points you get, the more weapons and abilities you unlock.