The principal liturgical table or structure at which the Eucharist is celebrated; historically a major focus for carved stone, relief, ornament, and surrounding sculpture.
An altar is the sacred table or structure at which the Eucharist is celebrated. Historically altars have provided one of the primary architectural settings for Catholic sculpture: carved fronts, reliefs, reliquaries, saints, angels, tabernacles, canopies, and altarpieces may all form part of the ensemble.
Etymology
From Latin altare, “altar.”
Sculptor Notes
A sculptor designing for an altar must understand liturgical function before ornament. Sightlines, access, candles, vessels, tabernacle placement, celebrant movement, and the hierarchy of the sanctuary determine where sculpture can project and how strongly it should command attention.
References
https://www.metmuseum.org/art/collection/search/475525