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 different styles and 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 as they dry.
Murals today are painted in a variety of ways, using oil or water based media. The styles can vary from abstract to trompe-l'œil (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.