POP3 and IMAP are two different types of email management accounts or "protocols". If your email is POP3, then you would have to change the type of protocol you're using to IMAP through your Internet Service Provider (ISP). These are the basic differences:
POP3 - "Post Office Protocol". With a POP3 e-mail account, your e-mail messages are downloaded to your computer and then eventually deleted from the mail server depending on how the account is set up.
IMAP - "Internet Message Access Protocol". With IMAP, you have access to mail folders on the mail server, and you can store and process mail without downloading it to the computer that you are working on.
That said, you can receive and send email from both types of accounts on multiple computers. Setting up POP3 to do that is a little more involved and requires a little more housekeeping because the same emails will be downloaded to all of the computers that the POP3 account is set up on even if it's deleted from one. Because of that most folks that want to be able to use multiple computers to access their email employ an IMAP email account so that their mail is always synchronized between computers.
Ultimately how you want to set things up is your choice, however, if you want to switch from POP3 to IMAP you'll probably need to deal with your ISP. It's not all that hard, but if you haven't done something like that it's best to let the experts take care of it.
Here's another article that might help:
How to set up POP3 and IMAP Email Accounts on the iPad | MyAppWorld.com