It is possible. What your friend is talking about it using Apple Mail as a “front end” for Google mail.
But first, some explanation is in order. Apple Mail is what’s called a POP mail program. POP stands for Post Office Protocol, and what Apple Mail does with POP s is retrieve mail from a server and download it to your Mac. Gmail is different in that it is Web-based email, which means you don’t use an email program for it; you use a Web browser (like Safari), and all your email stays at Google.
The advantages of a POP mailer is you download your email and you have it on your Mac all the time and can read it and write replies without needing to be connected to the Internet. Another advantage with Apple Mail is that you can retrieve email from several different accounts at the same time with Apple Mail and POP and keep all your email in one place.
Of course, the advantage to Gmail is that you can get to your email anytime you are away from your Mac and just have an Internet connection with any Mac or PC, so it doesn’t matter if you have your MacBook with you or not with Gmail.
But you can combine the two in a way, if it suites the way you work. And the advantages are you can use your GMail account and another email account in Apple Mail at home at the same time, but when you’re traveling, you can still use the Gmail web interface just for Gmail.
The best thing to do is follow Google’s instructions on how to enable POP for your Gmail account and get it set up in Apple Mail: Apple Mail 3.0 – Gmail Help. Read through the instructions and print them out if you need to.
Be aware of one setting in particular: whether you leave mail on the server or delete it. You may want to go ahead and leave copies of all your email on the server, so when you use Gmail in the web browser, you have copies of all your old email in Gmail, as well as on your Mac.