What is the identity of the 3 men who visited Abraham while he was sitting in front of his tent in the hot afternoon?

Remember that Abraham called their spokesman 'Lord' ( this title is only used to refer to God). Initially, the passage says that God appeared to Abraham and he saw the 3 men.

Also, we saw that it was 2 of them that later went to Lot, what happened to the other person?

What do they signify?

Pls help me if you know the answers