In agreement with bm. The domain (eg google.com) handles many services and the www kind of says which service it is using (www, mail, smpt, pop, ftp...). Of course, as www traffic is probably the most common kind, servers will most likely know what is expected, and act accordingly. Many servers are configured to redirect traffic from (eg) google.com to www.google.com. One reason for this is ...
Hostname is an attribute of a system stored locally on that system. "Computer name" is what Windows uses to refer to the hostname. A subdomain is a DNS concept. In DNS, domain names (domains for short) can be authoritative or non-authoritative - if they are non-authoritative, that means another server "handles" that domain. So in a domain such as www.mysite.invalid - one thing that could ...
Edit: to answer your original question, yes, any member of www-data can now read and execute /var/www (because the last bit of your permissions is 5 = read + exec). But because you haven't used the -R switch, that applies only to /var/www, and not to the files and sub-directories it contains. Now, whether they can write is another matter, and depends on the group of /var/www, which you haven't ...
It may not be the best example. On my website, Firefox does not add the www prefix. But a better example is my faculty website, which only works with the www prefix. Type ace.tuiasi.ro in chrome and it goes to www.ace.tuiasi.ro and it works, now type ace.tuiasi.ro in firefox, and it goes to ace.tuiasi.ro and it does not work (because they didn't configured their DNS correctly). Hope this is a ...
That's no standard, both "www" and "www1" are simply subdomains under the "schuh.co.uk" domain. Websites can be configured to have any number of subdomains, named pretty much however the webmaster or owner of the website wants. Subdomains in the form of "www" followed by a number sometimes indicate that the website is using a cluster of web servers for load balancing. In that case, "www1 ...