In general, an alter is a physical place were sacrifices are made to gods.
In the Old Testament, altars were places were animals were sacrificed to God as offerings or in payment for one’s sins. These sacrifices needed to be repeated again and again because people sinned again and again.
Alternately, altars were sometimes constructed to commemorate an event, agreement, or promise. Here their purpose was more like a monument, used to remind people of what happened.
Key verse about Altar: The Lord appeared to Abram and said, “To your offspring I will give this land.” So he built an altar there to the Lord, who had appeared to him (Genesis 12:7, NIV).
A lifelong student of the Bible, Peter DeHaan, PhD, wrote the 1,000-page website ABibleADay.com to encourage people to explore the Bible. His main blog and many books urge Christians to push past the status quo and reconsider how they practice their faith in every area of their lives.