An altarpiece is a carving, painting, sculpture, screen or decorated wall made for a Christian church altar, the table at which mass is said. They vary enormously in size and conception, from tiny portable pictures to huge structures embracing the arts of architecture, sculpture and painting. Normally, the altarpiece rests on the altar, but it is also found behind or even above. The centre of the altarpiece features a depiction of Christ, the Virgin Mary or a saint, with the side panels generally showing scenes relating to the life of the central figure. These are presented in chronological order and can be read like a comic strip. The backs of the side panels are almost always painted, giving a finished aspect to the altarpiece when closed. Sometimes panels are attached along the bottom; this is referred to by the Italian term 'predella'.
Predella: A subsidiary picture forming an appendage to a larger one, especially a small painting or series or paintings beneath an altarpiece.
Altarpieces divide into two main types: the reredos, which rises from ground level behind the altar, and the retable, which stands either on the back of the altar itself or on a pedestal behind it. Many altars have both.