A monumental canopy over an altar, shrine, or tomb; in Catholic art the term is especially associated with Bernini's bronze canopy over the papal altar of Saint Peter's.
A baldacchino is a ceremonial canopy erected over an altar, throne, shrine, or tomb. It developed from textile canopies into permanent architectural structures. Bernini’s colossal bronze Baldacchino in Saint Peter’s is the most famous sculptural example.
Etymology
From Italian baldacchino, originally a rich cloth from Baldacco, the medieval Italian name for Baghdad.
Sculptor Notes
The baldacchino is a total-work problem: columns, entablature, drapery references, heraldry, angels, ornament, and the void beneath the canopy must form a single spatial composition. It demonstrates how sculpture can define sacred space without becoming a wall.
References
https://www.metmuseum.org/essays/gian-lorenzo-bernini-1598-1680