According to Moses, the author of Exodus, the cherubims are like angels with wings that reach out and cover a special seat called the mercy seat. They face each other and look towards the mercy seat, showing how they protect and guard it.
Exodus 37:9: And the cherubims spread out [their] wings on high, [and] covered with their wings over the mercy seat, with their faces one to another; [even] to the mercy seatward were the faces of the cherubims.
Exodus 20:4 prohibits making graven images, whereas Exodus 37:9 describes a crafted cherubim as part of the Ark's design.
Exodus 20:4: Thou shalt not make unto thee any graven image, or any likeness [of any thing] that [is] in heaven above, or that [is] in the earth beneath, or that [is] in the water under the earth: