Cartridge(s) basically means the needles. There are many brands/kinds to choose from. Shure, Ortofon, Stanton, Numark all make them.

See below for Cartridges or "Carts".
www.musiciansfriend.com

thanx konix. yer a big help. but are they the par that holds the needles? do you buy new cartridges every time you need a new needle? or do you put needles in them? and what are the differend advantages of having different needles? do they do different things?

Typically when you buy a pair of cartridges, the needle is already preinstalled, although not always. As I said, there are dozens of different kinds. Some are designed for mixing, some for scratching, some are sutible for both. Some have a higher output than others, some are more for deep bass, some for crystal clear highs, Ortofon makes a pair specifically desgined for timecode vinyl (i.e. SSL's control record). There's just too many to explain so I suggest you serach Google for more info.