Experience System is a rating system wherein it will compile every battle ratings of the player thus defining him how go he is (Don't let the experience fool you as you don't really know if he is good or not)
Experience will appear in your profile at the same time in the score board (sheet whatever you prefer to call it). Simply it is just a battle rating. There are ways to gain and lost experience points
Ways to Gain Exp Points
Finish campaign level in difficulty (Easy, Normal, Hard and Impossible) finish it in easy will earn you 1, Normal for 2, Hard for 3 and Impossible for 4 if you a difficulty higher then the lower difficulty will be unlocked automatically and when you reset your campaign the points will be gone too. You cannot earn experience points if a cheat is on.
Multiplayer Kills- Every kills will earn you 1 point.
Capture the flag- Capturing a flag will earn you 5 pts. if retrieving is possible then you will earn 2 points for retrieving your flag or killing the carrier
Your team win- 1 Point
Capture the point- Point captured will earn you 3 pts, Defending it will earn you 1 point
Someone rated your map- will earn you 0.1-0.5 depending on the rating
Kill Death Ratio- Your kill death ratio multiplied by 2
Losing Experience Points
Death Count- You will lose 1 point