SD card

Secure digital (SD) cards are flash memory (non-volatile) memory cards used in the Wii and other Nintendo's consoles like the Nintendo 3DS, Nintendo DSi, and Nintendo DSi XL for data storage.

Use for the Wii[]

Stores additional downloads from the Wii Shop Channel library.
In the Photo Channel, the player can insert a SD card from a camera, allowing them to do various things, including puzzle games with video, slideshows with any photos, etc.
Store saved game data for Wii games.