Ranks indicate how much training or experience a character has with a given
skill. Each
skill has a number of ranks, from 0 (for a
skill in which a character has no training at all) to 23 (for a 20th-level character who has increased a class
skill to its maximum rank). When making a
skill check, a character adds his or her skill ranks to the roll as part of the skill modifier.
The rules assume that a character can always find a way to learn any
skill. However, the GM can impose limits depending on circumstances and a given situation.