The game stars a motor bike (There are several to choose from). The bike has a rider on it, who races other riders. The game has very precise physics, but is still more of an arcade racing experience than a simulation one. It may have licensed gear and over 30 real tricks, but it's still based on Excitebike. The most important of your controls is using the Z-button to boost. On ramps, you can double tap this boost to go clear bigger jumps and get more air.
In the racing genre, the motor bikes are as important as the tracks. Excitebike 64 has 20 of them. Some of them are realistic stadium tracks that you might find at some Motocross event. Others are obscene wacky tracks with giant jumps and hidden shortcuts. Even if you don't like any of these, there's still a track editor, so that you can make your own. That way you'll only have yourself to blame, and blame you should.
Now the details. The game supports an optional expansion pak. You don't need to have it to play the game, but it just looks better with it in. You can race with up to 4 players, or participate in other modes. One of them has you doing stunts. Another has you playing soccer with motorbikes.
Finally, where would these game revivals be without the original game locked away? Yes, if none of the above satisfies you like the original NES game did, you can play that too, right off the cartridge.