An altar was a kind of table or platform where sacrifices of animals or other offerings were made to God. Several different kinds of altars are mentioned in the Bible:
1. Israelite altars that were used for making sacrifices
(a) Stone altars built in the open air, such as those mentioned in Genesis and elsewhere in the Old Testament
(b) The altars for making sacrifices in the Tabernacle and in the Jerusalem Temple
2. Israelite altars that were used for purposes other than making sacrifices
(a) The altar for burning incense in the Tabernacle/Temple, including the altar mentioned in Revelation, where prayers were offered and incense was burnt
3. Pagan altars
In the entries that follow, different altars are described. However, in many verses it is uncertain exactly which altar is intended. This is especially true of events in the Tabernacle complex or the Temple, where either the altar for sacrifices or the incense altar may be intended. Many languages have a generic term for an altar or a ceremonial platform that can serve many purposes. Where there is no term for a place of sacrificial offerings, translators may need to use a descriptive phrase or borrow a term. See Stone altar for further discussion.