Printed Circuit Board (PCB) is a fundamental electronic component, widely used in varies electronics and related products. PCB sometimes are called PWB(Printed Wire Board) which are often used in Hong Kong and Japan before, now less and less people use it. Actually there is difference between PCB and PWB.
In western countries, the traditional name is PCB, but in east countries, there are some unique names, in China mainland it is called PCB but in Taiwan often called circuit board. In Japan it is call electronic base board but in South Korea it is called base board.
Before PCB appears, the electronic components are connected directly by using wires (nowadays we can also see this such as some simple Physic experiments). But it is too difficult and unstable, yet too expensive, so engineers thought they would add some wires in non-conductive base material and metallic conductor. Later on, after improving and improving, we see the popular PCB.
Currently, among the methods of connecting electronics components, PCB is definitely NO.1 choice.
Technically, PCB means a conductive product that produced following designed pattern and constituted by printed components and printed circuits on non-conductive base material.(IEC60194); PWB, means a conductive product that produced following designed pattern and printed circuits, without components, on non-conductive base materials.(IEC60194).
PCB and PWB are all called printed board, but normally PCB can replace PB and PWB.
So by definition we can tell PCB involve with primary PCB design, manufacturing (including testing), components assembly.
Today the industry has been divided into three smaller industries: PCB design, PCB manufacturing and PCB assembly. So from this point of view, PCB is a typical OEM/ODM product, and normally when we talk about PCB manufacturing, we mean the board manufacturing, not designing and assembly.