What are the…
also known as: שרפים (Hebrew) / sarap or seraph (singular)
These are Heavenly beings (cherubim / “living creatures”) who assist God, but they are distinct from angels. Their form seems to be somewhat human-like, with the addition of six wings. Their size is not mentioned. They have hands and feet, they speak, they fly, and they are holy and in very close proximity to God.
The verb used to describe these Heavenly “living creatures” may hint that they glow brightly. The face of the prophet Moses glowed brightly following his close proximity to God’s glory on Mount Sinai. When Moses came down from Mount Sinai, and the people saw that the skin of his face was shining like a bright light, they were afraid to come near him. Moses had to coax them to come close to hear his message from God.
When Moses finished speaking to them, he put a veil over his face. Then the people were not so afraid to have him walk among them. But whenever God came to speak to him, Moses took off the cloth covering his face. And when he came out and told the Israelites what he had been commanded, they saw that his face was radiant. Then Moses would put the veil back over his face.
Seraphim stood above Him, each having six wings: with two he covered his face, and with two he covered his feet, and with two he flew. And one called out to another and said,
Then one of the seraphim flew to me with a burning coal in his hand, which he had taken from the altar with tongs. He touched my mouth with it and said, “Behold, this has touched your lips; and your iniquity is taken away and your sin is forgiven.” —Isaiah 6:6-7 NASB
This word (seraph), in the original Hebrew שָׂרַף, is used elsewhere only of the “fiery serpents” (Numbers 21:6,8; Deuteronomy 8:15—compare Isaiah 14:29; 30:6) that were sent by God to inflict on the people the righteous penalty for their evil actions.