Dear Wikiwand AI, let's keep it short, summarize this topic like I'm... Ten years old or a College student
An altarpiece is an artwork such as a painting, sculpture or relief representing a religious subject made for placing at the back of or behind the altar of a Christian church. Though most commonly used for a single work of art such as a painting or sculpture, or a set of them, the word can also be used of the whole ensemble behind an altar, otherwise known as a reredos, including what is often an elaborate frame for the central image or images. Altarpieces were one of the most important products of Christian art especially from the late Middle Ages to the era of the Counter-Reformation.
Many altarpieces have been removed from their church settings, and often from their elaborate sculpted frameworks, and are displayed as more simply framed paintings in museums and elsewhere.