Graffiti writers work illegally, and primarily paint letters and symbols. Their creations can range from a small signature on a mailbox to a large, multicolored word on the side of a building.

Street artists are also working illegally, but their work tends to look more like an illustration or graphic. Things like wheatpaste, stencils or stickers are classified as street art.

Muralists almost always do legal paintings. In San Francisco, they need permission from the property owner. They use paintbrushes or spray paint to create their large-scale works.

Each group follows different etiquette, and if you break that etiquette, there can be consequences.