This tool will traverse the url you specify, parse the html, and then check that each URL linked on that page is GET-able. Any linked pages that start with the same url fragment as your original request will also be parsed.
So the following example will test all links on all pages that it finds on that site:
$ ./linkcheck http://some.url.com/
Whereas the next example will only test pages with url's that begin with http://some.url.com/some/sub/section/
$ ./linkcheck http://some.url.com/some/sub/section/