An altarpiece is a painted wood panel, usually placed on the altar in a church. Altar-pieces come in many forms. One of the most common types of altarpieces is the triptych, so named because it is made up three connected panels. Often, the panels of a triptych are hinged and the outer panels can be closed like doors, revealing additional exterior paintings. An altarpiece with only two panels is called a diptych, while an al-tarpiece with many panels, such as the Ghent Altarpiece (discussed in the following section), is known as a polyptych.