The PCB layout is normally defined using a software that allows you to position each component on the PCB and interconnect the components. This is visually done on a PC using a CAD package like Eagle. This creates the PCB layout. It can also be done using transfers directly onto the copper clad PCB, but I never had great success with this method.
Once the layout has been defined in the CAD package, it has to somehow be transferred to a real piece of PCB. This can be done as described above. At home we print the layout onto a piece of transparency(the film). This transparency is then pressed tight against a copper clad PCB coated with photo sensitive resist, and exposed under an Ultraviolet light for the correct amount of time so that when it is developed (special developer solution) the bits of copper we want to retain, remains covered with the resist.
The PCB is the etched by putting it in an etching solution that eats away the bits of copper that is not protected by the resist,leaving only pads and traces of copper.
Optionally the PCB can then be tinned to make soldering easier and protect the copper.
Optionally on the component side a silkscreen is used to mark and label each component.
