Experience Points XP resemble the obtained experience of the character. During the game players can gather experience points (XP) in several ways. The most important way is to complete chapters of the story (for example by defeating important enemies or uncovering essential parts of the story).
In each chapter there are ways to gather bonus XP, for example by completing side missions, finding additional secret information about the story line or completing the chapter in a certain way.
Experience points can be used to increase the field values on the Talent Tree Sheet. See the link for additional information. Unused XP can be registered on page one of the character sheet (bottom right corner).