Church altars are not only practical in a religious service, but they are also a symbolic aid to remind worshippers of their faith.
The Bible records the first use of an altar in the book of Genesis in the account of the flood. This account concludes with Noah building an altar of sacrifice to the Lord as an act of worship, celebrating God's promise not to destroy the earth with a flood again.
Today in Protestant churches (typically Baptist), the church altar is usually made out of wood and is used for altar calls. The altar call concludes the sermon and invites those who wish to respond to the sermon to come kneel at the altar and confess their sins to God.
In the Roman Catholic Church, altars are made of stone and represent both the church and Christ. In Protestant use, the altar serves as a reminder of needful sacrifice to God as well as Christ's sacrifice for sinners.
For Christian denominations, the altar is often used to hold the elements of the Lord's Supper or Communion or used as the table for the Eucharistic meal.
In several Eastern religions the altar is used as a place for worshippers to set their offerings of food, incense, and money.