The Disc Channel allows users to play disc-based Wii titles (and in some cases, Nintendo GameCube software) that is inserted into the Wii system’s disc drive.
In Mario Kart Wii, asphalt is slightly shiny, reflecting a band of light ahead of the player. This is implemented cleverly by leveraging something that the Wii is already doing, allowing it to not need to use any sort of additional lighting or post-processing.