A WAD file is a file archive containing .APP files, which can be extracted and installed on a Wii

Wii

The Wii is a home video game console released by Nintendo on November 19, 2006. As a seventh-generation console, the Wii primarily competes with Microsoft's Xbox 360 and Sony's PlayStation 3. Nintendo states that its console targets a broader demographic than that of the two others...

 gaming console

Video game console

A video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device to display a video game...

. They often contain information for the Wii, such as System Menu, IOS, Channels etc. Although they are mainly used to install custom channels and IOS, they have also been linked to piracy, as users can install pirated WiiWare

WiiWare

WiiWare is a service that allows Wii users to download games and applications specifically designed and developed for the Wii video game console made by Nintendo. These games and applications can only be purchased and downloaded from the Wii Shop Channel under the WiiWare section...

 and Virtual Console

Virtual console

A virtual console – also known as a virtual terminal – is a conceptual combination of the keyboard and display for a computer user interface. It is a feature of some operating systems such as UnixWare, Linux, and BSD, in which the system console of the computer can be used to switch between...

titles through the use of WADs. WADs are generally installed using the homebrew application WAD Manager.