IMAP or Exchange accounts will sync mail folders with the server. POP accounts won't. SMTP (Simple Mail Transfer Protocol) is a protocol/server most most providers use to handle outgoing mail, and is standard for both IMAP and POP accounts.
The IMAP and POP protocols have to do with handling mail syncing/copying between a computer client and the server. SMTP sends your email on it's way to the recipient; although that is probably a gross over simplification it will have to do, because thats about all I understand about it myself.