What is "braze-on"

A braze-on is the name for any number of parts of a bicycle which have been permanently attached to the frame. The term "braze-on" comes from when these parts would have been brazed on to steel frame bicycles. Braze-ons continue to be so called even though they may be welded, glued, riveted, or moulded into the frame material, depending on the material itself and the connection method used elsewhere on the frame.