The only truly silly question is one that goes unasked. EMT is short for Electrical Metallic Tubing The NEC definition is......
An unthreaded thin-wall raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed utilizing appropriate fittings.EMT is generallymade of steel (ferrous) with protective coatings or aluminum (nonferrous).
It is available in 1/2" through 4"trade size and available in 10 foot lengths.
[This message has been edited by txsparky (edited 06-07-2003).]
Emt is used as a raceway, the same as Rigid and Intermediate conduit. The biggest differences are the EMT is to thin to be threaded and it is not as durable in corrosive areas. Emt is mainly used indoors, but is also used outdoors above grade.