Potestas
Players use their characters to interact with each other's characters and the game setting as presented and supervised by the GM. A character is a persona used by a player during the game: it is also a set of values that have meaning in the game system being used.
Potestas defines a character using the following categories: Characteristics, Skills, Abilities, Stature, and Cosmetic Details.
Characteristics define the inherent physical and mental qualities of a character. All characters will have a modifier for each Characteristic that indicates their level of talent or aptitude. Your GM may or may not allow characters to change their Characteristic modifiers during the course of play.
Skills are specific applications of Characteristics: Skill bonuses are added to the character's appropriate Characteristic modifier and may be improved if the player wishes. Your GM may set a limit on the maximum bonus allowed for any one Skill. Skills can be innate (mostly physical skills like being accurate or avoiding being hit, but also some mental skills like noticing hidden things) or require specific learning or life experience (mental skills like being literate or well educated).
Abilities are things most characters simply cannot do. Examples include being able to hurl fire from your hands or change into a werewolf at night. Most Abilities do not have a modifier, but some do. Your GM may or may not allow characters to have certain Abilities.
Stature indicates the character's degree of life experience, importance and prowess. Characters of higher Stature are better at what they do and can do more impressive things than characters of lesser Stature. Your GM will indicate what Stature characters should have at the start of play.
Cosmetic Details are those things that add definition to a character but that do not necessarily have impacts on game system mechanics. Examples include eye and hair colour, gender, height, weight, age and race. Your GM will indicate if any Cosmetic Details have game impacts: for example, being a Human or a Kattar has no inherent game impact, but Elves are magically-powerful immortals and their exceptional nature has game impacts. In some cases, Cosmetic Details may be defined by other mechanics: for example, all characters who can use Sorcery are left-handed.