How can I manipulate the vanity element in a url node? This is more of a general question, because I know I can get by with vanity={2}, but a lack of proper understanding is holding me back from truly mastering my community server site.
I've seen examples like this in the SiteUrls.config:
<url name="post_InPage_Old" path = "{0}/ShowThread.aspx#{1}" pattern = "(\d+)/ShowThread.aspx" vanity="{2}?PostID=$1^PermaPost=$2^UrlName=permalink" page="ForumUrlHandler.ashx" />
but the format confuses me. What are the $1 and $2? Where are they set?

