What is push mail - particularly in mobile phone?

Can anyone explain to me what is push mail? How is it different from the other e-mails? How to use it in mobile phone?|||Push e-mail is used to describe e-mail systems that provide an always-on capability, in which new e-mail is actively transferred (pushed) as it arrives by the mail delivery agent (MDA) (commonly called mail server) to the mail user agent (MUA), also called the e-mail client. E-mail clients include smartphones and, less strictly, IMAP personal computer mail applications|||Push mail is email that updates as soon as a message comes in, rather than updating every 10 minutes, etc. I think you need IMAP email, rather than POP-based, in order to have push abilities.