What is the difference between seraphim and cherubim?

In Christian theology, seraphim are the angels nearest to God; cherubim sit just below them.

Seraphim have three pairs of wings; cherubim, one or two pairs.

There are nine choirs of angels in all.

From highest to lowest, they are: seraphim, cherubim, thrones, dominions, virtues, powers, principalities, archangels, and angels.