It is important to distinguish between the tool and the content.

Creating your own WADs from games you legally purchased is possible but technically complex, involving "nopping" and extracting content from the Wii Shop servers (which are now largely defunct and archived).

Never, ever install a WAD that replaces the vWii System Menu (often named vWii System Menu 4.3U/E/J). Standard Wii system menus are different. Doing this creates a full vWii brick (black screen on launch).

If you install a WAD with a corrupted banner (the animated channel icon that appears on the menu), the vWii may freeze upon booting the System Menu. Because the vWii menu loads automatically when entering Wii Mode, you may be locked out of the vWii entirely.

A WAD is a file format used by Nintendo’s Wii system to package channels, system files, and installable content (for example, Wii Shop Channel titles, IOS files, and custom channels). Installing a WAD typically writes files to the console’s NAND or emulated storage so the content behaves like an officially installed channel or system component.

The appeal of vWii WADs is straightforward: Convenience.

Here’s a helpful feature regarding vWii WADs (for the Wii U’s virtual Wii mode):