There are basically two types of email service. The first is iMap, where you access your email normally through a browser. The mail is all stored on the server and you don't have any mail stored on your local machine. A pop3 server works basically the opposite: you have a program on your computer called a mail client which reaches out to the server, logs in, and then downloads all of the incoming mail.
You can find your pop3 mail server by searching for your maill service and "pop3 server." An example might be:
"MyMailService pop3 server."
For your imap server it would be just the name of the website you use to access it such as Gmail.com
HTTP is the hyptertext markup language used for coding web pages and wouldn't pertain to the questions regarding your email.