An electrical conduit is a tubing system used for protection and routing of electrical wiring.
RSC is a thick-walled threaded tubing, usually made of coated steel, stainless steel or aluminium.
EMT, sometimes called thin-wall, is commonly used. EMT itself is not threaded, but can be used with threaded fittings that clamp to it. Lengths of conduit are connected to each other and to equipment with clamp-type fittings. EMT is more common in commercial and industrial buildings than in residential applications. EMT is generally made of coated steel, though it may be aluminium.