A Gerber file (also known as artwork) is a 2-D graphical representation of a single layer of a PCB. A typical design will have individual Gerber files for each layer (e.g., top copper, bottom copper, top silkscreen, bottom silkscreen, top soldermask, bottom soldermask) of a PCB.
This walkthrough goes through the process of creating a PSoC® 4100S Plus prototyping board PCB footprint.