Plasma cutting is a process that is used to cut steel and other metals of different thicknesses. In this process, an inert gas (in some units, compressed air) is blown at high speed out of a nozzle. At the same time an electrical arc is formed through that gas from the nozzle to the surface being cut, turning some of that gas to plasma.
The plasma is sufficiently hot to melt the metal being cut and moves sufficiently fast to blow molten metal away from the cut. This thecnology can be use to cut all metals, because they are electrically conductive.