A decorative frontal covering or panel on the front of an altar, historically made in textiles, precious metal, carved wood, stone, mosaic, or relief.
An antependium, or altar frontal, covers or decorates the front face of an altar. It may be textile, metalwork, mosaic, carved wood, stone, or relief and may display Christ, saints, angels, heraldry, or Eucharistic symbols.
Etymology
From Latin antependere, “to hang before.”
Sculptor Notes
The frontal is read almost as a horizontal relief panel. Because the altar itself remains a functional block, sculpture should reinforce the frontal plane and central axis without making the liturgical furniture visually unstable.
References
https://www.metmuseum.org/art/collection/search/475525