A WAD file for Super Mario Galaxy 2 packages game content (channels, titles, or game updates) for Wii consoles and emulators. Below is a high-level description of what such a WAD might contain and steps to create/use one for legitimate backup or homebrew purposes only.
System IOS: Internal operating system files required to run hardware. Super Mario Galaxy 2 Wad File
Channel Forwarders: Many users create or download "forwarder" WADs. These are small shortcuts installed to the main Wii Menu that allow a player to launch Super Mario Galaxy 2 directly from an external drive (via tools like USB Loader GX) without having to first open a separate loader application. Super Mario Galaxy 2 Wad File Overview A
Conclusion
Installation
Using a homebrew app like WAD Manager or YAWMM, you select the .wad file. The app decrypts, verifies (or bypasses signature checks), and writes the contents to the Wii’s NAND flash memory. No disc swapping: Launch directly from the Wii System Menu