Layer 2 Switch - I build a table of MAC addresses, you tell me which MAC you want and I switch your traffic accordingly. I am better than a hub because I has a table.
Layer 3 Switch - I know where things go and can priortize yo shit. Fuck what you think know, I tell you what you know. Because I can now operate at switch speed, Layer 2 switches are obsolete for all but the cheapest of businesses.