Seraphim convey a different concept to cherubim ('the living' which appear in Eden, on the kapporeth of the ark, in the oracle of the temple and in Ezekiel; and whose name appears again, borne by the man Kerub, who came back from captivity).
Saraph  the Hebrew word behind the English translation, occurs seven times in the Piel, the active and intensive form, and once more, making eight, as a man's name.
Serephah  occurs thirteen times and is translated by the KJV and by Young as burn or burning, but not a normal burning; it is evident from the occurrences, and the link in one place to brimstone, that it is an intense burning.
Together, there are twenty-one references, a significant number in scripture.
The same word as appears here, seraphim, is elsewhere translated fiery serpent [KJV] but in those other places they are not directly related to the throne of God. Here they are.
It is clear that, here, saraph, corporately, represent a concept. The literal translation [Young's Literal] reads :
Seraphs are standing above it: six wings hath each one; with two covering its face, and with two covereth its feet, and with two flieth.
The very wording blends the imagery from plural to singular; and we are not told, in any case - in this place - how many there are.
Two wings cover the face, two cover the feet. The mode of progress is obscured and the identity is obscured and their sight is obscured. And what does the obscuring - is something heavenly; the wing. The wing is a means of heavenly motion. And here, that which propels in a heavenly manner, is the very thing that obscures.
These things are mysteries; they require revelation; and he to whom it is revealed is he who shall interpret. But interpratation is off-topic, here, so that is all I shall say.
Saraph : Num 21:6, Num 21:8, Deu 8:15, Isa 6:2, Isa 6:6, Isa 14:29, Isa 30:6
Saraph, the man : I Chron 4:22
The Piel Form