Skill point

Skill points are points awarded to the player character when reaching a new level of experience. The player is then free to allocate the points to whatever skills he feels are in need of improvement.

Certain books, traits and perks give the player a skill point bonus for a specific skill as well.

Fallout 3
The number of attainable skill points (without books, and not including what your skills are at character creation or your tagged skills) is 428. Combined with the Comprehension perk and every Vault Boy Bobblehead, you can achieve a 100% stat in ALL of the skills, though it might take some time searching the wasteland for everything.

The Broken Steel add-on raises the level cap to 30, and therefore adds a potential 230 extra skill points to the game, for a total of 658 to divide amongst all your skills.