The Crew calls "specs." There are five of them and they are swappable on the fly, offering the player control over his or her racing destiny.
A new official blog post today details these five specs. Street specs are versatile jack-of-all-trade cars, Dirt specs are great for off-roading, Perf specs sacrifice maneuverability for speed, Raid specs are terrific for exploring rough environments, and Circuit specs are built for top-notch technical racing.
If a player has not attained a certain spec yet and a mission requires it, the game will provide a loaner for the duration of the mission.