Further subtitled "On the Internet, without an address, no one can scream back at you."
If you don't want to read any farther, here's what you probably want. The address you should use (for example, as the "Email Address" field in SquirrelMail under your personal information options) is 'your account name'@'the web site you use to access email minus the www. part'. For example, if you go to www.greeley.org and log in as hod, you would want to use email@example.com.
Now, what that really means to an email program is "deliver this message to user account hod in domain greeley.org". There's lots of machinery behind doing that.
SquirrelMail is one of those really cool tools that a bunch of people out there decided to build, just because they felt like it. It's a lot of work, so think nice thoughts about these people when you use it. If you want to know who they are (and more about SquirrelMail), go to the SquirrelMail site.
SquirrelMail is what has become known as a webmail tool. Simply put, it allows you to access your email using a web-browser instead of a separate email program. This means, at least in theory, you should be able to access your email from most any machine connected to the web. Yup, that's right, walk into that Internet cafe and email away within moments. Well, that's the theory anyway. More on why that might not be the case as we go, but it should work in a lot of situations.