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, es:Pedro Nel Gómez, David Siqueiros, José Orozco or Rufino Tamayo) . There are many techniques. The most well 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.
The Mission District of San Francisco, California has numerous murals.
Murals today may be 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). Wikipedia