Experience Points (EP or XP) are a concept derived from AD&D. Essentially the Games Master awards XP to characters to represent that experience gained from achieveing goals and overcoming obstacles. When the character has accumulated enough points he may rise in level, or be able to use the points to improve his skills or characteristics.

It is important to realise that the awarding of XP is not a competative thing, a player who gets more in a session has not 'won' and no one is competing to get more than others, indeed many GMs simply give the same to all players at a game, while others allow the players to decide how much they should get. Rather the slow accumulation of XP and the resultant imporvement of characters represents the effort the players put into developing their characters.