These tools allow you to install WAD files from an SD card directly onto your Wii’s NAND (internal memory). This is where the phrase becomes popular: users extract WADs from their own purchased games or, more commonly, download them from websites that host pirated copies of Virtual Console and WiiWare titles.
A WAD file is an archive format used by the Wii to install "channels" to the system menu. This includes everything from the Mii Channel to digital games and system updates. In the homebrew world, WADs are used to install: wii wads free