TTTC is an addon to TTT2 that adds custom secondary abilities, called classes, to each player. TTTC doesn't ship with any classes, but provides an easy to use interface. Classes feature two parts: a passive ability that is given once the class is set and an active ability that is triggered on a ability keypress for a certain amount of time combined with a timeout after the usage.
To learn more about creating a class check out our docs!