Free Nintendo Emulator
Emulate Nintendo GameCube and Wii consoles using this free emulation software. Get all the fun of these classic consoles through your computer.
The job of an emulator is essentially to pretend to be the hardware of a particular system so that software (in this case, video games) from that system can be played on modern hardware. Dolphin specifically emulates Nintendo GameCube and Wii consoles. Beyond simply playing these games, Dolphin actually provides certain enhancements to your emulation experience, such as graphical improvements. Dolphin can run games from the original discs or from a ROM dump of that game, however the developers are very clear that acquiring ROMS of games you don't own is illegal, and that even creating ROMs of games you do own is questionable.
As Good As It Gets
There aren't many problems with Dolphin over other options out there. Sure, some games won't run, and other's don't run as well as they would on the original hardware. But for the most part Dolphin is stable, looks great, and is completely free. It's hard to argue with that.