Dear 100 Hour Board,
What's the difference between 'http://whateversite.com' and 'http://www.whateversite.com'? Are they not the same page on the same computer? I've seen cases where the two are different, like my own site right after I update something (not on my own computer, I use an ISP ).
p.s. hopefully my hypothetical example website above doesn't show up as a real link. If so, please disable it. Thanks!
The www specifies the webserver for whateversite.com. If you only type in whateversite.com it assumes www.whateversite.com. You can specify mail, ftp, etc. by typing mail.whateversite.com or ftp.whateversite.com, etc. (e.g., mail.google.com can be used to quickly access your gmail account). Adding those at the beginning of the web address will allow access to the services whateversite.com may offer. However, not all websites will offer things such as ftp and mail.
Polly is sort of right... -ish. The webserver (the actual piece of software that handles http(s) requests and decides how to respond to the user's browser) can be configured in a number of ways and then there are DNS configuration options as well. You'll notice that "theboard.byu.edu" is configured to respond to anything occurring before "theboard.byu.edu", however your session will be a new session, which gets a new cookie (so it looks like you've logged out). For example you can go to: "silly.theboard.byu.edu" or "non.sense.theboard.byu.edu" and it all shows up the same and for the most part works just fine. If you go to "mail.theboard.byu.edu" you will notice that we have redirected that page (using DNS controls) to point at the Google servers hosting our email.
The convention used for a long time was that you host websites using the "www" prefix. But, there's no requirement to do so. For instance, slashdot.org and digg.com are two popular sites that don't use the "www" prefix. So there are no hard and fast rules about what they mean. If you so desire you could configure your server to display something different depending on the sub-domain (the part that comes before the "example.com" piece). This practice is extremely common. The Board is hosted at "theboard.byu.edu" which is a sub-domain of "byu.edu". Route Y can be accessed by going to "ry.byu.edu".
So hopefully that clears some stuff up for you. Oh and by the way, the appropriate way to provide example web addresses is to use the "example.com", "example.net", and "example.org" domains which exist solely for this purpose. Sadly, many people who should know better fail to use the example domains properly.
So your question should read "What's the difference between 'http://example.com' and 'http://www.example.com'...."
-Curious Physics Minor