Question: The chief ruler Antionah asked Alma a question about the “cherubim” on the east of the Garden of Eden. What are cherubim?
Answer: A cherub is an angel with specific assigned duties.
“What does the scripture mean, which saith that God placed cherubim and a flaming sword on the east of the garden of Eden, lest our first parents should enter and partake of the fruit of the tree of life, and live forever?” (Alma 12:21)
Source: 400 Questions and Answers About the Book of Mormon by Susan Easton Black, p. 152