Cherubim is the plural form of Cherub, guardian angels. First mentioned in Genesis 3: 24

After he drove the man out, he placed on the east side of the Garden of Eden cherubim and a flaming sword flashing back and forth to guard the way to the tree of life.

They are also placed on the Ark of the Covenant to guard the content.

The Cherubim is the second highest order of angels and is a strange being. It has four faces, man, ox, lion and eagle. The Cherubim are guardians and guard  God's Throne. God placed Cherubims with flaming swords to guard the Gates of Eden after the Fall.