This document discusses different types of pipe fittings used to join pipes and tubes, including screwed, welded, flanged, flare, compression, and soldered fittings. It separates fittings into those suitable for thick-walled pipes like screwed, flanged, and welded fittings, and those for thin-walled pipes such as flare, compression, and soldered fittings. Each type of fitting is then briefly defined.