SMT is a technology to assemble electric components upon printed circuit boards.
SMT has the advantage of producing smaller components at a lighter physical weight.
It reduces the need to drill holes into the printed circuited board.
In simple, single-layer circuits, this technology enables simpler automatic assembly (each component is placed only on one side of the board) which enables higher production rates.
In multi-layer circuits it is possible to assemble components on the reverse side of the printed circuit board as well.
Using less material at soldering points (reduces the resistance and induction of the connection points, enabling work at higher frequencies).