SMT: Stands for surface-mount technology. It is normally used to create an electrical circuit; however it is very different when compared to other circuit technology. SMT is where the electrical components are mounted onto the printed circuit board or PCB.
In the electric industry the SMT has really overtaken the through-hole technology because it is much more efficient for different purposes. The through-hole system threads wire into holes in the circuit board, whereas SMT mounts it onto the surface. These two technologies are still used today, as SMT isn't as suited to semiconductors or large transformers.
Many people choose to use SMT over other electric technologies because it is smaller than the through-hole alternative. The main reason for this is because it has no leads or very few of them. You will also find that it has small pins and flat contacts which make up the body. Small balls of solder may also be found on the main circuit board.
There are many advantages to using SMT over through-hole techniques, and the major one is the density of each component. SMT has a very small component density when compared to components per area and it also has many more connections per component so this makes it very efficient in terms of space used and connectivity.
Another bonus of SMT is that it has a lower cost and it doesn't take much time at all to set up for the production. It doesn't need as many holes drilled into the assembly and there are very little errors in terms of component placement. These can be corrected with ease as well because the surface tension of the solder pulls it into place with the solder pads so this makes it ideal for a huge variety of different purposes.