can someone tell me what no$gba is for

hi just reading through many posts and quite a few go on about no$gba... it may be stupid but i can patch games, and get alot of ppl coming to me to get me to patch games. but i just wanted to know what no$gba is, i assume that it is an emulator, but is it to use on the pc or ds? ???

you use it on your PC

thanks.