POP is Post Office Protocol. This is how Mail servers on the Internet communicate with our clients and other servers to get and deliver mail to you.
IMAP is Internet Message Access Protocol. It is a different way of delivering mail. Does basically the same thing as POP, but the Mailboxes are live. As soon as a new email hits the IMAP inbox, your client on the Mac knows about it. This one is great for use with multiple Macs, iPhones
, keeping the same mailbox on all of them in synce.
So, you use POP if you have 1 Mac and do not roam around with it. You use IMAP if you have more than one Mac/iPhone/Smart Phone and you want them all to stay in sync with the email.
As far as wiping, in the trues sense of the word, yes. It will erase everyting on the hard drive, leving you with a clean empty drive. Then you re-install OS X, update it, and then re-install Applications, setup your printer, email and other stuff.
Not fun from that point unless it was absolutely needed.
You would have to backup everything and then do the wipe. Then you can put stuff back (most of the time, some apps require installing).