The word atonement carries with it the idea of the just, holy, righteous side of God’s nature being satisfied. God’s law required death as the penalty for sin. When God saw the death of the innocent sacrifice, he was satisfied that the demands of his law had been carried out. Sacrificing an animal on an altar did not take away the sin. Man was still sinful. The sacrifice only pictured what was necessary for sin to be forgiven—death and shedding of blood. The blood provided an atonement or covering for sin.” –The Stranger on the Road to Emmaus by John R. Cross

Out of the tabernacle’s six pieces of furniture, so far we’ve looked at the ark of the covenant, the table of “presence bread”, the golden lampstand, and the incense altar. We now come to the fifth piece of furniture where animal sacrifices were burned: the brazen altar.

(bible-history.com)
When the common Israelite approached the tabernacle with his sacrifice and passed through that entrance gate he found that between him and the tabernacle structure stood an altar with a priest waiting beside it. The altar was square in shape (foursquare). Its length and breadth were exactly the same as the height of the white linen fence around the court 5 cubits (7 1/2 feet). Its height was 3 cubits (4 1/2 feet) and it was made of acacia wood overlaid with bronze with horns at each corner.

(bible-history.com)
The first thing a worshipper met when coming to the tabernacle to offer a sacrifice was a white linen fence that surrounded the tabernacle. This created a courtyard where the priests ministered. At the west end stood the tabernacle proper. The east end held a thirty-foot entrance to the enclosure where the priests met the people coming to offer sacrifices. The priest would inspect every animal carefully to make sure it was acceptable. To identify with the offering, the worshipper would lay his hand on the animal’s head (Lev. 1:1-9). Then the priest would slay the animal and offer it on the brazen altar (Lev. 1-7).

One Way to God

There was only one way to get to the altar of God because there was only one entrance gate to this enclosure. Likewise, there is only one entrance to God. The “gate” is Jesus Christ (John 14:6; 10:9).  Many think that every way is acceptable to God in our pluralistic society, but Scripture teaches otherwise (Prov. 14:12; Matt. 7:13-27). Forgiveness from sin and fellowship with God can only be attained through His Son.

Below is a summary of the significance and symbolism of the brazen altar.

(Source: SlideShare from The presence of_the_lord_v2)

For more on the significance of the tabernacle sacrifices and how they point to Jesus Christ, I found the following post from the Tabernacle Place helpful: The Brazen Altar. Also, The Bronze Altar from Bible History Online offers a more detailed post. Blessings!