A plasma cutter works by channeling a jet of concentrated air through a nozzle. Before this air leaves the nozzle though, it passes across an electrical arc. This arc superheats the air, making a jet of extremely finely aimed, powerful and hot air.
This air is in fact so hot that it can cut metal. That is a plasma cutter!
By the way, it has nothing at all to do with blood plasma! So don’t worry about that, there isn’t going to be a jet of blood shooting out the end of your plasma cutter. (If there is, definitely contact your manufacturer, because that’s not right!)