A phono cartridge is a small device attached to a turntable that converts the mechanical vibrations of a vinyl record into electrical signals. It contains a stylus, or needle, that tracks the grooves of the record, picking up the sound information encoded in them. The cartridge then sends these signals to an amplifier, allowing you to hear the music through speakers. There are two main types of phono cartridges: moving magnet (MM) and moving coil (MC). MM cartridges are more common and generally easier to replace, while MC cartridges offer higher sound quality but can be more expensive and require specialized equipment.