A mural is a painting on a wall, ceiling, or other large permanent surface.
Murals of sorts date to prehistoric times such as the paintings on the Caves of Lascaux in southern France, but the term became famous with the Mexican "muralista" art movement (Diego Rivera, David Siqueiros, or José Orozco). There are many techniques. The best-known is probably fresco, which uses water soluble paints with a damp lime wash, a rapid use of the resulting mixture over a large surface, and often in parts (but with a sense of the whole). The colors lighten when dried.
Murals today are painted in a variety of ways, using oil or water based media. The styles can vary from abstract to trompe l'oeil (a French term for "fool" or "trick the eye"). Today, the beauty of a wall mural has become much more widely available with a technique whereby a painting or photographic image is transferred to poster paper which is then pasted to a wall surface.
Murals are significant in that they bring art into the public sphere. Due to the size, cost, and work involved in creating a mural, muralists must often be commissioned by a sponsor. Often it is the local government or a business, but many murals have been paid for with grants. For artists, their work gets a wide audience that otherwise might not set foot in an art gallery. For the city, it gets beautified by a work of art. Murals exist where people live and work and affect their daily lives.
Murals are a relatively effective tool of social emancipation or achieving a political goal. Murals have sometimes been created against the law or have been commissioned by local bars and coffeeshops. Often, the visual effects are an enticement to attract public attention to social issues.
World famous are the murals in Mexico, New York, Philadelphia, Belfast, Derry and Los Angeles  which have functioned as an important means of communication for members of socially, ethnically and racially divided communities in times of conflict. They also proved to be an effective tool in establishing a dialogue and hence solving the cleavage in the long run. State-sponsored public art expressions, particularly murals, are often used by totalitarian regimes as a tool of mass-control and propaganda. However despite the propagandist character of that works, some of them still have an artistic value.