When configuring your email on your computer, you will get a choice of whether to use IMAP or POP... but which should you use?
Both IMAP and POP will allow you to access your email, but they do it in different ways.
POP simply downloads your email to your computer, deleting the email from the mail server. This means that your email resides on your PC and is good if you are limited for space on your email provider's mailbox server space as it will keep downloading mail as you check from your computer, emptying your account on the mail server.
Although you can configure your email program to keep a copy on the mail server, this is not the default behaviour.
IMAP is more like a 'cloud' service, allowing you to read and manage while your mail stays on the mail server. Therefore, IMAP allows you to keep your email across multiple devices in sync. If you delete mail on one device, mail will be deleted from the server and therefore on all devices. If you read mail on one device, it will show as being read on all your devices. If you loose your phone, you should be able to recover your mail from the mail server as it doesn't live on the phone.
In short, if you are using multiple devices it is best to use IMAP.
If you only have one device checking mail, or you struggle with space in your mailbox on the mail server, it may be best to use POP.