The altar in a church is the table on which the sacrifice of the Mass is offered. For many centuries the altar was placed in the sanctuary against the rear wall, and the structure rising up against the wall was called the reredos or altarpiece. It was frequently decorated by painting or sculpture. When the structure is removed from an old church to a museum, the artwork is called an altarpiece.
Hugo van der Goes
Oil Painting
My notes on the altarpiece; hopefully this is what you mean by "characterize"Reflects Catholic beliefsCreated for the monastic hospital order Saint Anthony of IsenheimSaint Sebastian is on the left, Saint Anthony is on the right, lamentation is on the predellaSaint Anthony and Saint Sebastian are associated with miraculous curesIt is meant to encourage devotion and provide hopeThe right panel:Depicts the five temptations as monstrous creaturesThe grotesque man has ergotism which was known as "Saint Anthony's fire"They didn't know what caused "Saint Anthony's fire" until the 1600sIt was a major illness at the time that was treated in this hospitalThe left panel:The meeting of Saint Anthony and Saint Paul
This is one of the most popular subjects in Christian art. It has been painted by hundreds of painters over the centuries to be placed in a church or chapel as an altarpiece. The Virgin Mary sits on a throne holding baby Jesus. A few or many angels gather round to adore the child.
San Giacomo dell'Orio Altarpiece was created in 1546.
Fano Altarpiece was created in 1497.
Bentivoglio Altarpiece was created in 1488.
Martinengo Altarpiece was created in 1516.
Gozzi Altarpiece was created in 1520.
Barbadori Altarpiece was created in 1438.
Paumgartner altarpiece was created in 1500.
Vallombrosa Altarpiece was created in 1500.
Bardi Altarpiece was created in 1521.
Ghent Altarpiece was created in 1432.
San Luca Altarpiece was created in 1453.
San Zaccaria Altarpiece was created in 1505.