What are the differences between POP and IMAP

(Note: The following is really about POP3 and IMAP4.) 
 Basiclly, IMAP is a more complex protocol that is more suitable for users who frequently access their e-mails from more than one machine. 
 
 
 POP is a much simpler protocol that basically just supports listing, reading and deleting messages, beside authentication. The rest is handled by the e-mail client (such as Thunderbird). 	 For POP , there is no way to “push” a e-mail back to the server, except forwarding it to the same account. 	 
 IMAP has built-in support for folders. Users can move e-mails around local (client-side) and remote folders. 	 It also supports storing states (e.g. read/unread status of a e-mail message) on the server. 	 Fewer e-mail providers support IMAP . e.g. Gmail supports POP but not IMAP (yet).