A footprint is called a "land pattern", which is mainly used during PCB layout so that an electronic component gets soldered onto the PCB conveniently. Furthermore, footprint still consists of several layers information, including the copper lands, silkscreen (the text and shapes you see when looking at a PCB), solder mask, solder paste, courtyard, etc.

Apart from that, when it comes to the characteristics of a footprint, I have to say, it is various and based on the mechanical dimensions and tolerances of component, that's to say, the corresponding standard is used to create the footprint and design requirements.

In a nutshell, with the help of complete footprint, PCB designers tend to understand relevant components and do PCB layout easily.