Oh cool, I kind of got interested in this stuff last year and read a short book about it.
A track is a series of challenges (corners), separated by straights, which give you a breather to recover and prepare for the next corner. In a circuit, you get multiple attempts to learn and improve your execution of those challenges. I've been thinking about ways to incorporate that into other genres as well.
https://danielprimed.com/old_site/speed-boost-the-hidden-secrets-behind-arcade-racing-design/
The author also wrote some 500-600 page breakdown of Wario Land 4, which I also bought, but haven't dared to start reading yet.