URLs, Domains and Protocols
Created | Updated Jan 28, 2002
The term URL either stands for Universal Resource Locator or Uniform Resource Locator. There's a bit of confusion as to which is correct, but it certainly stands for one of them. What a URL is, is a pointer to a resource on a network - the internet in particular. Usually you will see a URL look like this:
http://www.bbc.net.uk/h2g2/guide/
Let's take that apart, shall we?
http:
That's the protocol you're using, in this case it's http, but it could easily be https, ftp, nntp, gopher or in theory, a number of others. Then we have two forward slashes (//) to separate the protocol from the rest of our URL.
www.bbc.net.uk
This is the name of the host that we're looking it. Think of it as the name of the computer on which the web pages that we want are residing on. You can have lots of names for the same computer, for example, www.bbc.co.uk point to the same place as the .net.uk address.
The .net.uk part just shows that it's a domain registered for the UK, much like any .net address, but for the UK.
The bbc.net.uk part is the actual domain that the BBC own. You look these domains up and find out who owns them and where:
The www part before the domain is actually the computer host name, or at least an alias of the computer.
Anyway, the next part is /h2g2/guide/
That's the path. That's telling the website exactly which pages or files you want to look at. If you don't specifiy a file within a directory, the website will try to find a default page for you, and send that to you. Usually these default pages are called index (as in index.html) or default (as in default.asp).
But let's not forget that URLs can be used for other protocols, for example:
So, to recap on the main points:
bbc.net.uk is not a URL. It is either a hostname or a domain - and in fact it is both. You can point a domain to a computer without a hostname. In some cases, it may also be a company name - there are lots of dot com companies who use their domain as their company name. I won't mention any here as it might be viewed as advertising.
www.bbc.net.uk is also not a URL. It is a hostname. It is not a domain.
Further reading can be done at the following resources:
World Wide Web Consortium guidelines on addressing:
http://www.w3.org/Addressing/
Internet Engineering Task Force, RFC 1738
http://www.ietf.org/rfc/rfc1738.txt
Internic (Domain Names) FAQ
http://www.internic.net/faq.html
