Fresco is any of several related mural painting types, done on plaster on walls or ceilings. The word fresco comes from the Italian word affresco [afˈfresːko] which derives from the Latin word for "fresh". Frescoes were often made during the Renaissance and other early time periods.

Buon fresco technique consists of painting in pigment mixed with water on a thin layer of wet, fresh, lime mortar or plaster, for which the Italian word for plaster, intonaco, is used. A secco painting, in contrast, is done on dry plaster (secco is "dry" in Italian). The pigments require a binding medium, such as egg (tempera), glue or oil to attach the pigment to the wall.

Source: Wikipedia