Gmail is a very popular e-mail server nowadays. People like being able to access their e-mail, organized just like they want, from anywhere they might be. Before gmail there wasn't many good interfaces for that, but google showed that it's possible to have a reasonable e-mail reader running on top of a browser.
Unfortunately, when you're at your home computer, you are able to have whatever program you wish running, and suddenly the browser reader isn't that nice anymore. Using it means opening up a bloated browser (lightweight ones won't work, or at least not nearly as nice) just for e-mail. Since I'm running a slow computer, I really can't afford to have a heavy browser always running; I was almost forgeting about having an organized web interface and starting to use the POP3 interface. But then I bumped into libgmail, which exported a lot of gmail's interface to python. As soon as I found it I started hacking my own terminal-based program. I called it gmailreader.
Using gmailreader you don't need a web browser at all! You can read, compose and archive e-mails, you can see the e-mails by labels. And the best of it all, you do all that from your terminal. Oh! Another good thing! You can use your favorite editor to edit your e-mail -- how wonderful is that? After you're done reading your e-mails with gmailreader you'll find out that all that archiving, reading, spam reporting, etc you did on gmailreader happened to the gmail interface as well. That means you don't have to choose between a organized web interface or reading e-mails outside a browser; you can have both.