What does a NTSC/PAL Selector do? Whatz the difference?

its for people who play import games, people in north america have different types of tv's, than people almost everywhere else (i think there's one asian country that has the same as us). and if you try to play a game without changing its output (northamerica -ntsc/ everywhere else-pal), the colors will be all messed up.. its basically for people who like to play import games.. it doesnt remove mod protection or anything.