A printed circuit board (PCB) is used in electronics to build electronic devices. A PCB serves two purposes in the construction of an electronic device; it is a place to mount the components and it provides the means of electrical connection between the components. In many modern devices the PCB forms an intrinsic part of the structure of the product.
Surface mount technology allows components to be soldered directly onto the surface of the PCB rather that soldered to it using traditional techniques. This allows for a greater density of components, which either increases the number of components in the same space or allows you to make the same board smaller. Surface Mount technology is much finer and therefore requires a higher quality of manufacture.