"A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, or traces, etched from copper sheets laminated onto a non-conductive substrate. Alternative names are printed wiring board (PWB),and etched wiring board." from Wikipedia - Printed Circuit Board. In its more pure form it is simply a normally flat plastic or ceramic substrate in which alternative layers of insulators and conductors are grown sequentially to form isolated conductive paths to transfer signals and current in and out of electronic components.

PCB (printed circuit board) layout optimization to avoid EMI (electromagnetic interference). A PCB layout should not only strive to prevent the emission of noise but also have good noise immunity from outside sources. One should have an understanding of potential sources of noise and have a strategy for dealing with these problems.

By John Isaac, Mentor Graphics [ Courtesy of Assipe ]
In today’s competitive electronics industry, getting to market ahead of the competition can mean the difference between a successful product and one that misses its market window. Design cycle time plays a big part in determining a product launch schedule and the PCB layout portion of this process often is called upon to make up for early design phase schedule slips. One designer and one computer at a time can be a limiting factor.

As in any large, mature industry, the PCB industry has undergone significant evolution since its beginnings.

If you don't have the budget enough to buy an ESD "gun", you can make it by yourself, exclusively in order to verify the quality of your Printed Circuits.