Your skills represent a variety of abilities, and you get better at them as you advance in level.
At each level, you get skill points that you use to buy skills. Your class and Intelligence modifier determine the number of points you receive.
To make a skill check roll
1D20 + skill modifier
(Skill modifier = skill ranks + ability modifier + miscellaneous modifiers)
The higher the roll, the better. You’re either trying to get a result that equals or exceeds a certain Difficulty Class (DC), or you’re trying to beat another character’s check result.
Skill Ranks: A character’s ranks in a skill is based on the number of skill points the character has invested in the skill. Some skills can be used even if the character has no ranks in the skill; doing this is known as making an untrained skill check.
Ability modifier: The ability modifier used in the skill check is the modifier for the skill’s ability (the ability associated with the skill’s use). The key ability of a skill is noted in it’s description and on the Skill Table.
Miscellaneous Modifiers: Miscellaneous modifiers include bonuses provided by feats and class features, and penalties such as the ones associated with the non-proficient use of armor, among others.