The Nintendo GameCube (GCN/NGC/GC) is a video game console made by Nintendo which was available from 2001 to 2007. It uses a 32-bit CPU. The Wii was also a video game console made by Nintendo, but it was available from 2006 to 2013. It uses a similar CPU and general architecture as the GCN. There are a few emulators for each of the two consoles, but the most prominent one is Dolphin, which is in this book.
Dolphin is a GCN and Wii emulator and is generally considered the gold standard of emulators. It supports multiple controllers, connection methods, general settings, etc.