Cherubim are heavenly beings placed by God, with a flaming sword, at the east of the garden of Eden after Adam and Eve were sent out, to keep the way to the tree of life so that they could not return and partake of its fruit and live forever (Alma 12:21; 42:2-3).
Alma the Younger refers to them twice in his teaching. In Alma 12:21 he raises the scripture that says God set cherubim and a flaming sword on the east of Eden lest the first parents enter and partake of the tree of life, concluding that there was no chance they should live forever. In explaining the matter to his son Corianton, he says that after God sent the first parents from Eden to till the ground, he placed at the east end of the garden cherubim and a flaming sword “which turned every way” to keep the tree of life; the man had become as God, knowing good and evil, and the guard was set lest he take of the tree, eat, and live forever (Alma 42:2-3).
The text does not describe their appearance. The fuller iconography of multiple faces and wings found in Ezekiel’s visions does not appear in these passages.