Seraphim is the plural of Seraph. They are the highest ranking of angels and have 6 wings as described by Isaiah 6:2:

 I saw the Lord sitting upon a throne, high and lifted up; and His train filled the Hekhal (sanctuary). Above Him stood the Seraphim; each had six wings: with two he covered his face, and with two he covered his feet, and with two he flew."

The Seraphim is the highest order of angels and is a strange looking being. Isaiah noted that the Seraphim had six wings. The Book of Revelation does not mention Seraphim by name but refers to Isaiah's creatures with the six wings. The Seraphim constantly surround the God's Throne and sing or chant what in the Orthodox and other Eastern churches would be the Trisagion.

Lucifer was a seraphim, but evidently had twelve wings.