Webmail, or web-based email if you prefer, refers to an email clients which is used via a web browser such as Internet Explorer. On the other hand, desktop mail refers to email clients such as Microsoft Outlook, which receive and store email directly on your computer. Both of these options have their advantages and disadvantages, depending on the personal needs of the user.
For users who wish to receive their email on multiple computers, or may travel frequently, a webmail account may be the way to go. Since webmail opens via a web browser, it is possible to receive your email from anywhere on the planet as long as you have a computer with an internet connection.
The catch of course, is that without an internet connection, webmail clients cannot be accessed, which can be very inconvenient. With desktop mail programs, emails are saved directly to your PC once they are received, so email that has already been received can be accessed again without an internet connection. A problem with this, however, is that years of use without cleaning out your cache of received emails can cause speed issues on a computer. Desktop email users should be aware of this issue and delete mail which is no longer needed.
If your computer is often accessed by multiple users, a webmail client might be useful to allow a greater degree of privacy, as it cannot be accessed by anyone who does not have the password. However, it is possible for webmail to be hacked too, particularly if your password is not strong enough.
Examples of webmail clients are: Gmail, Hotmail, and Yahoo. Examples of desktop mail clients are: Outlook Express, Windows Live Mail, and Thunderbird.