Skill

A skill is an action your character can perform, it's success is affected by how much you have train the correct skill and by your natural capacities (for example, having an high Dexterity makes you better at tumbling). As you increase in level you can spend points into skills in order to be more succesful at it.

Skill points
As your character increases in level they will gain skill points. The rate at which you gain points is dependant on your class, your intelligence modifier and your race.
 * Humans have an additional 4 bonus skill points at 1st level and 1 each level after. Example: A Human Rogue with 18 intelligence will have 52 skill points to spend, at 1st level, 13 each level after.

Skill points can be distributed into skills depending on your class. When spending your skill points, it will cost one point to increase a skill's rank by one if it's a class skill, however, it will cost you two skill points to increase its rank by one if it's a cross-class skill. Note that you can only invest skill points in Disable Device or Open Locks if you have at least one level of rogue.

You can find the number of skill points for each class on the classes page. Note also that one of the human's primary racial benefits is additional skill points compared to other races.

Skills and Difficulty Class
When using a skill, your are most likely trying to defeat a score. For exemple, when a rogue is trying to disarm a trap, he must beat a certain score to disarm the trap, that score is the difficulty class.

Active skills
When using active skills, you are always trying to beat a DC. Whether you are intimidating a foe or searching for a secret door. Most of the time, you will have to roll a dice, sometimes you won't. When a dice is rolled, a natural 1 or a natural 20 does not grant an automatic failure or success.

The formula to beat a DC is: 1d20 (when applicable) + skill modifier (Skill modifier = skill rank + ability modifier + miscellaneous modifiers).

Passive skills
When using passive skills, you are not necessarily trying to beat a DC. For example, when jumping, simply your skill modifier is taken in account to determine height of your jumps. Most of the time, you won't have to roll a dice when using passive skills, sometimes you will. When a dice is rolled, a natural 1 or a natural 20 does not grant an automatic failure or success.

The formula to beat a DC is: 1d20 (when applicable) + skill modifier (Skill modifier = skill rank + ability modifier + miscellaneous modifiers).

Source of miscellaneous modifiers

 * Enhancements
 * Feats
 * Spells
 * Race
 * Equipment