I read the page and I'm still fuzzy on the concept. What does it do for me? Thanks.
I guess it test your urls at least. From the above link:
NOT MATCHED: account/email/
NOT MATCHED: account/register/
My understanding is that it walks all the links on your site and records the times and response codes for each URL. It then compares these URLs to the site's routing information and notes routes that are not reachable.