Trevor is one of the main protagonists and playable characters of Grand Theft Auto V as well as a filthy individual due to his appearance. At some point during the late 1980's to early 1990's, Trevor entered the military as a pilot, and retired in the early 2000's. Not too long afterwards, he met Michael. Both men realized that they wanted to earn money by performing heists, and both men became successful in doing so. Some point afterwards, both men had a falling out, causing a major rift in their friendship.
By the events of GTA V, Trevor is in his mid 40s living in a filthy trailer in a desert, with his best friend Ron living next to him. Trevor ended up spending all of his robbery-earned money, so he then needs to get back into performing heists and running errands to earn money, by which times he meets Michael again, who introduces him to Franklin.
While Michael and Franklin have the special ability to slow down time, Trevor's special ability is to deal out extra damage, or take less damage, and he can also perform a unique melee attack when the special meter is activated.