particle emmitters

now, i dont want a link to a huge tut that will tell me nuthin, so i just want a simple answer "what are particle emmiters anwhat do they do"?

Particle emitters are a data entry that tells the engine to emit certain things out, either models or small billboarded texture images

Particle emitters are anything from smoke to the 'trail' that the Shade leaves when he moves.
see the smoke in Cookie's avatar? that's a particle emitter on the model.