Metal Inert gas welding  (MIG) uses a continuous wire feed as an electrode and a special gas mixture to protect the weld.  Since the wire fed electrode is continuous, this is a faster process than arc welding.

Tungsten inert (TIG)  welding uses a non-consumable tungsten electrode, a special gas mixture and a seperate filler material..  It is especially suitable for thin materials and can be used on almost all metals.  It is often used where strength is a priority such as high-end bicycle frames and aircraft applications.

Plasma cutting is a process used to cut a variety of metals.  A special gas is blown at high speed out of a nozzle.  An electric arc is formed simultaneously through the gas.  This turns the gas into plasma.  This is hot enough to melt the metal and blows the metal away from the cut..  Very fast, clean cuts are produced.