What is POP What does it do Apple iPad air

POP or Post Office Protocol is an outdated method of receiving emails, useful if you only have one device with which you download emails, too often it doesn't work as if you delete emails they're not deleted from the account.

Imap is so much better as you have direct access to the email account & anything done on one device is reflected on all devices using the email account with the same imap settings.

In Ye Olde Days, POP was the only way to receive emails and worked much like the quaint people from the Post Office that used to deliver mail even on Saturdays. There was a single copy of each mail, which was copied over to your client when you connected and removed from the server. Leaving that only copy on the device you connected from. Makes for real inconveniences in these days where we all carry multiple gadgets to connect to the Internet from. Most mail providers still offer it for those Luddite diehards out there, but it has been thoroughly obsoleted.

Nowadays the Internet Mail Access Protocol (IMAP) offers a much more flexible alternative. Works like a window into the contents of the server, where your mail now stays until told otherwise. So if you consult it on your phone, tablet or computer, it stays there and stays the same, in a device-independent manner.

If you still have any POP-configured mail account, would be beneficial to convert to IMAP for ease of use. However, be careful when deleting old POP accounts since the old mail they contain resides, in general, only on the device they are configured and will be lost if provisions are not taken beforehand. Holler back with more details if that is your case, so we can help.

You can't delete POP. It is an adjustment, a configuration in an email account. Once all the old mail found in the storage allocated to that account in the device you are using has been saved elsewhere (I'm considering that you might want to save it, else ignore this sentence), you delete the account, which removes all traces of it from the device but not from your provider's server.

Then you create a new instance (Settings / Mail, Contacts, Calendars / Add Account, pick the appropriate profile for whatever mail provider you are using), which will normally auto configure itself as IMAP. You will need, of course, your email address and the access password in the configuration process. You can also set up as many accounts as needed; for instance I have 10 in my iGadgets, mixed iCloud, MS Exchange (corporate Office365, really) and GMail.