There are two different classes of pads, surface mount technology SMT pads and thru-plated hole technology TPH pads
SMT Pads
SMT pads are cover areas on only one side of the PCB. Electronic parts adhere to the pads using the solder on the pads.
TPH Pads
TPH pads have copper areas on both the top and the bottom sides of the PCB. In addition a hole is drill through the circuit board to connect the top pad area to the pad area on the bottom. The electronic pin for the part is inserted through the hole and often the sides of the hole are plated with copper. However, if you are making a single sided board then the copper will most likely be placed on the underneath side of the PCB unless the PCB is being made with SMT parts, in which case you will need to have the copper pads on the side of the board where you mount the SMT parts, in other words the top side.
You can add the following types of pads.
Pads