TrackMania – I recommend Nations Forever if you’re starting out; it’s free and Nations was the “meta” environment (different environments have different physics) for a long time, so there’s a fuckton of custom content for it.
As for what it is: it’s like the racing genre’s Quake equivalent. It’s also like super hot wheels. And it’s like Mario Maker. You make all kinds of crazy tracks with it, like Mario Maker. The tracks feature all kinds of wall rides, half-pipes, jumps, loops, and so on, with nothing more than inertia holding you to the track; like hot wheels. And finally, like Quake (and Mario Maker), the high-level players are bat shit insane.
This is the game where you get people who can hit a jump at just the right angle so they thread the needle through a series of holes barely larger than the car while travelling at speeds well above 300mph (welcome to TrackMania, I don’t think there’s a speed cap). They also do it using keyboards. Seriously. High-level TrackMania players use keyboards, not gamepads or, god forbid, racing wheels.
All of that said, no pressure because you’re mainly racing yourself, even in multiplayer. You’re trying to get the best time on a track, and multiplayer is basically the same, except your time is being compared with everyone else’s. There isn’t even any vehicle collision (strangely, there’s an option for it, but it doesn’t seem to do anything).