In addition to the post @Faru made,
Menuhax is a exploit for running homebrew that takes advantage of a bug in theme loading made by yellow8
Browserhax is an exploit for running homebrew that takes advantage of a glitch in the browser that was patched in v9.9
OOT3Dhax is an exploit for running hombrew that takes advantage of a glitch in how The Legend of Zelda: Ocarina of Time 3D loads the game (or something like that).