The Stig is a mystery race car driver who appears on a TV show called Top Gear. He wears a full racing suit that is all white with a helmet that has a dark visor, so you can't see his face. He's named after a character from a show called "Stig of the Dump" who was also mysterious.
The Stig does not talk, but he drives cars incredibly well! He's so good that he tests expensive and fancy cars to see how fast they can go around a track. The hosts of Top Gear do not know who he is because he's kept secret, and they like to make jokes about him being a robot or an alien.
Some say The Stig is played by several different drivers, but nobody knows for sure. That's part of the fun: trying to figure out who The Stig really is!