Rob touched on the importance of optimizing permalinks for searches but just to give you a general definition, a permalink is simply the static link to a post or blog entry. So if you wanted to link directly to Rob's comment in this thread you would use...
http://www.websitebabble.com/html-ja....html#post8330
And yes, I had to add (buy) a plug-in for this forum to make the permalinks contain the keywords from the thread title. Before I added the plug-in the permalinks were just
www.websitebabble.com/post24234.html for example.