IMAP and POP are two methods to access email. IMAP is the recommended method when you need to check your emails from several different devices, such as a phone, laptop, and tablet.
IMAP allows you to access your email wherever you are, from any device. When you read an email message using IMAP, you aren't actually downloading or storing it on your computer; instead, you're reading it from the email service. As a result, you can check your email from different devices, anywhere in the world: your phone, a computer, a friend's computer.
IMAP only downloads a message when you click on it, and attachments aren't automatically downloaded. This way you're able to check your messages a lot more quickly than POP.
If you want to access your email from multiple devices and synchronize the mailbox folders and data, then you should use IMAP.
POP works by contacting your email service and downloading all of your new messages from it. Once they are downloaded onto your PC or Mac, they are deleted from the email service. This means that after the email is downloaded, it can only be accessed using the same computer. If you try to access your email from a different device, the messages that have been previously downloaded won't be available to you.
Sent mail is stored locally on your PC or Mac, not on the email server.
A lot of Internet Service Providers (ISPs) give you email accounts that use POP.
Webmail accounts vs email apps
If you've used Gmail, Outlook.com, Hotmail.com, iCloud, or webmail.visuallink.com then you've used webmail. To get to your webmail account, you access the Internet and sign in to your email account.
If you have a PC or Mac, you've probably used a program like Outlook, Apple Mail, or Thunderbird to manage your email. Outlook, Apple Mail, and Thunderbird are email apps: programs that you install on your computer to manage your email. They interact with an email service such as Gmail or Outlook.com to receive and send emails.
You can add any email account to your email app for it to manage your email. For example, you can add webmail accounts - Gmail, Outlook.com, Hotmail.com, AOL, and Yahoo - to the Outlook or Apple Mail app to manage your email, and you can add work email accounts.