A staple gun is a mechanical device used to fire small metal staples into materials. It has a far stronger action than a paper stapler and is often used for more heavy duty applications, such as attaching paper or fabrics to wood.
A staple gun is an essential tool for the artist whether for putting drawings on the wall in an exhibition, or for stretching canvas over a boxed frame, it is an all purpose tool hard to do with out.
The most common style of staple gun uses a manual leverage/trigger system, if stapling repeatedly in succession this can take some effort and tire your hand, the alternative it a power operated staple gun which only requires the simple press of a button.
You can purchase a staple gun from any art supply store or framing supply store, however a wider range is usually available from hardware stores.