Parts of it were etched during the process of production. Those parts left become net-like thin traces, which are called conductor pattern, and are used to provide circuit connection for components on PCB.
(2) Name of two side:
On most common single side PCB, components are on one side, conductor pattern is on the other side. Then we would need to drill holes on the board, so that pins can put through the board to the other side.
Therefore, the both sides of PCB are called component side and solder side.
(3) Gold finger:
Gold finger is functioned to connect two PCBs. We usually insert the gold finger of one PCB to the proper slot of the other PCB.
(4) Solder mask and silk screen:
The green or white oil on PCB is called solder mask, which is functioned as dielectric protective layer, can protects copper traces and also can prevent components to be soldered at incorrect place.
On the dielectric layer, a layer of silk screen will be printed. Some words will be printed to show the position of those components. It is also called legend.