A Seraph, or Seraphim, is a six-winged angel. They are known to be the being closest to God. Some people say that a Seraph is a warrior of Heaven. It is known they use their bottom two wings to cover their "feet" (in the Old Testament "feet" referred to a person's genitalia), the middle two to fly, and the top two to cover their eyes in the glory of God.
The oldest interpretation of these angels had their bodies engulfed in flames, a representation of God's overwelming power.