Wonderful arts

Stencil graffiti, made famous by Banksy in the last 4 or 5 years, has actually been a form of street art for 25 years. You can use cardboard, paper or other forms of surfaces (such as plastics) to produced templated imagery and text. You merely cut around the design from your cardboard/paper/other surface, put then set this surface against a wall (for example), and roll-on paint or spray into the cut-out shapes.
In essence, the art of stencilling involves applying paint across a stencil to form a picture on a surface below. Sometimes multiple layers of stencils are applied on the same picture to add colours or create the illusion of depth.
There are myriad reasons for being a stencil graffiti artist. For some, it is a great platform to produce a political point. Many stencil artists value the PR that their artwork can acquire. Some merely desire their work to be seen. As the stencil stays unchanged during its use, it is easier for a stencil artist to rapidly copy what could be a complex piece at a very speedy pace, when equated to other prescribed tagging methods, so without question, there is also a strong promotional reason to get involved with stencilling.
Banksy has applied stencilling as a way to put a point across, often rather succinctly, providing the witness to work out that very point in their head. This is oftentimes why people love his artworks so much, as they force the viewer to reflect on the significance behind the artwork. Banksy artwork is now being reproduced on posters, t-shirts and graffiti art on canvas, such is the popularity of the street artist.