MIXERS
Every DJ needs a mixer. It is impossible to DJ without one. Basically a mixer is a machine that allows you to feed in different music sources, for example, a CD player or turntable. Then you can control the volume level of the input source and feed the final mix out to a tape deck and/or speakers.
There is a huge variety of different types of mixers to choose from. It depends on what you use it for and how professional you are as a DJ. Some mixers have two inputs, some of three, etc. Some have two crossfaders (a slider that allows you to change between two channels) but usually one. Some of the more expensive mixers (£150 +) even have digital sampling. With that, basically you can record a piece of a song or your voice in the mixer's memory (RAM) and play it back over and over again.