By default, WebCopy will only scan the primary host you specify, for example
http://example.com. By setting the sub domains option, you can include sub-domains, for example
http://demo.example.com. In additional to this, you can instruct WebCopy to include other hosts with completely different domain names, for example if the site you are copying makes use of a CDN.
Some project settings are ignored when crawling additional hosts, for example the crawling above the root URI