Gmail is Google's Web-based e-mail service. It was one of the first e-mail services to offer users 1GB of storage space for their e-mails at a time when others were offering just a few megabytes. Google's philosophy with Gmail is to aim for the needs of power users. That might sound like foolishly overlooking the much larger mainstream market, but it's actually preparing them for the future: given the increasing importance of Internet communications, an ordinary user tomorrow will face the same challenges as a power user today.
In the strictest sense, Gmail brings the paper-pushing productivity style of yesterday into the computer age. Thanks to Gmail's handy labeling feature, which is a big reason the service became so popular, most messages you care about can be already organized with labels automatically as they arrive. You can read and reply if necessary, and after that, it's a simple task to just plop messages into a giant archive with no pesky manual filing. They can then be retrieved easily via search or labels.
Also worth mentioning are the filters, which are automated tasks Gmail performs before you even touch your e-mail. Instead of having to manually move mail from your partner to a particular folder, you can set Gmail to attach the appropriate label to any message from that person. You can also set up any message that contains a particular word (or words) to be automatically labeled in a given way. This means organizational drudgery is down and findability is up. Filters can also forward, delete, and archive mail automatically. And when you set them up, it applies them to the existing archive, which helps ensure e-mail stays organized even years after you received it. Add to this Gmail's fast and thorough search functionality, and you have a free Web-based client worth checking out.