Abilities are, as the name suggests, skills that your character explicitly has learned or mastered. Instead of rolling for a skill set it’s always advantageous to use a suitable ability instead.
Abilities are always categorized in either of the three skill sets. If you are uncertain which ability belongs into which category of skill sets, the GM will decide for you.
The final value of your ability score will be calculated from the ability points you spent and the respective skill set score. The bonus you gain from the skill set score will be added to each ability, unless the player decides against it.
You can find detailed information on this in the exemplary character creation.
To look up:
The final value of the ability that is supposed to be rolled on consists from the points spent in the ability plus the values from the skill set score.
Example : Hartmut spent 200 points in Actions ( actions = 20 ) and 50 of these in woodcutting ( woodcutting = 50. His final value in woodcutting is calculated as follows: woodcutting 50 + actions 20 = woodcutting 70