Traction
Traction is the rear tyres' ability to put engine power down without spinning, and it decides how early a driver can accelerate out of a corner.
It matters most at slow corners leading onto long straights, where a fraction of a second earlier on the throttle carries all the way to the next braking zone.
It is not the same as grip in general: a car can have plenty of cornering grip and poor traction, which is a common complaint at circuits with tight, low-speed exits.