SMD is a component, SMT is a technology and process, one is an object, and the other is a non-object.
Different functions, SMD is used to place some simple lead components after the first automated machines are introduced, and SMT is a circuit pack that mounts leadless or short lead surface mount components on the surface of printed circuit boards. Even technology.
SMD; it is an abbreviation for Surface Mounted Devices, meaning: surface mount device, which is one of the SMT (Surface Mount Technology) components. In the initial stages of electronic circuit board production, via assembly is done entirely by hand.
SMT: It is a type of leadless or short lead surface mount component (referred to as SMC/SMD, Chinese called chip component) mounted on the surface of printed circuit board (PCB) or other substrate surface. A circuit-mounting technique for soldering assembly by means of reflow soldering or dip soldering.