This type of pcb can be used for both through hole and surface mount components. The complexity and density of components means much equipment has to use both sides of the Printed Circuit Board and better products usually supplement this with plated-through-holes where the copper connections go right through the connecting holes to the opposite side of the board. These all the way through the board connections make double sided PTH PCB a much more physically robust item.
Double sided pcb’s consist of two copper layer on a rigid base material, the two copper layers are not connected. Double sided pcb’s with plated through holes have two copper layers that can be connected by a copper plated hole, solder resist and idents can also be added.