Reredos. A carved or painted screen behind the altar. Very few medieval ones survive; those that do, are often not in their original churches, but brought in by an 18th century antiquarian or 19th century Anglo-catholic vicar. Their subjects, usually saints or the crucifixion, made them an obvious prey for the Anglican reformers of the 1540s. No evidence suggests that many survived to incur the wrath of the puritans 100 years later; Dowsing does not mention coming across any in his journal. The famous Thornham retable was originally part of the altarpiece at Thetford Priory, and spent the penal years in a barn. There is a pre-Reformation reredos at Barsham - but it is from an Italian church. Another fine one, although no longer behind an altar, is at Cavendish. However, it is possible that decalogue boards were painted over some of them.
Many churches have 19th century reredoses, produced under the influence of the Oxford Movement. They are of varying quality, and different ones appeal to the taste of different people. I am inclined towards the high camp of the 1870s, and so I favour the two at St Mary le Tower, Ipswich. More rural in feel, and one of the best of its kind, is at Gosbeck. Perhaps the finest example of a modern reredos is the Arts and Crafts Movement one at Kelsale; but this now stands at the west of the church.
Technically, the one of these on the high altar is a retable, although the distinction between the two is rather hazy.