You might also want to check out the trackback forum here at MT support.
Trackback is a system by which people can automatically generate links to their blog entries on remote sites. For example, you're surfing the web and you see an entry in an MT blog that you want to talk about some more
and you want people who visit that blog to come and read your entry as well. You could post a comment to the other blog with a link to your entry or notify the blogger about it in hopes that they'll provide a link to your entry. But that's a lot of work.
Trackback aims to take the work out of it. If the other blog has enabled trackback, then all you have to do is bring up your handy MT bookmarklet while viewing that other blog. You will automatically have an option to ping (notify) the other blog of your entry when you publish it. You'll see a notification during the publishing process that tells you it is pinging a certain URL. After you've done publishing your entry, you can click on the "Trackbacks" link for the entry in the other blog and you will see a link to your blog automatically created there.
Another way of using trackback is that somebody may have a category in their blog devoted to, say, book reviews. They will provide on their site a URL to ping for this category. Let's say you write some book reviews in your own blog and you want links to them to show up in the other blog. So you copy down the URL to ping. You can either enter it for an individual entry (in the URLs to ping section of the new entry screen) or you can set it up for an entire category of your blog. Again, when you publish entries, the other blog will be notified and a link to your entry will automatically show up there.
I hope this explanation makes some sense. If not, please do post again with your questions and I'll try not to be so confusing