Who is Athenian Townsmen from Protagoras and Meno and what is their importance?

The Athenian townsmen meet at Callias' house to hear Protagoras. These men include Callias, Paralus, and Xanthippes, sons of Pericles, Hippias of Elis, Eryximachas, Phaedrus, Pausanias and others.