Stencilling has actually been around for 25 years, even though many people think Banksy devised it. You can use cardboard, paper or other forms of media (such as plastics) to make templated imagery and text. You merely cut out the design from your paper/cardboard/other surface, put said surface onto a wall (example), then spray or roll-on paint.
In effect, the method of stencilling involves applying paint across a stencil to form an image on a surface below. It’s also possible to employ multiple layers of stencils to produce an illusion of depth or even add colours.
There are innumerable causes for being a stencil graffiti artist. For some, it is a great platform to shout out a political point. Many stencil artists treasure the PR that their artwork can acquire. Some just want their work to be viewed. As the stencil remains consistent throughout its use, it is easier for an artist to rapidly duplicate what could be a complex artwork at a very speedy rate, when equated to other conventional tagging methods, so without question, there is also a compelling self-promoting reason to choose stencilling.
Banksy has applied stencilling as a means to make a political statement, often quite succinctly, providing the viewer to work out that very point in their head. This is oftentimes why people enjoy his artworks so much, as they make the viewer think. Banksy artwork is now being reprinted on t-shirts, canvas and posters, such is the popularity of Banksy.