Very fun game. One of the flag ships in the Nintendo arsenal.
It's the standard racing game. You have 50, 100 and 150 class carts and bikes. You get unlocks by completing sections and special stuff in the game.
There's 4 basic areas to compete in, and each area has 4 tracks. So you start with 16 tracks. As you complete them you unlock other areas, each with 4 more tracks to compete in. Total race tracks is 32.
But wait, there's mirror mode, which flops all 32 tracks (note: FLOPS, not reverses). There's also a couple of "battle" modes with several other tracks.
Online play is awesome. You race against people from all over the world. There's even tournaments you can enter and submit your time. Most (all?) tourny tracks are REVERSED tracks.
I could go on, but suffice to say it's a "must have" game if you own a Wii. The multiplayer and online experience make it an exceptional game.