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What does WWW do?

The usual form of an internet adress is for example http://www.example.com. Sometimes I encounter pages, that have the www missing, like in this real world example:

https://service.discoplus.de/

Why is that so?

If I type in https://wwwservice.discoplus.de/ (with www) it asks me a security question and then rerouts me to http://www.discoplus.de/. So obviously internet adresses with and without www are not equivalent.

Thanks for any enlightening!

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you might want to see this: webmasters.stackexchange.com/questions/14457/what-does-www-do –  Christofian Jan 26 '12 at 1:43
    
You may also want to read this: "Why does my site only work with a www in the URL?": webmasters.stackexchange.com/questions/25071/… –  mvark Jan 26 '12 at 9:46
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marked as duplicate by Lèse majesté, paulmorriss, John Conde Jan 26 '12 at 14:32

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

2 Answers

The reason is this:

The domain is discoplus.de Anything before that:

service.discoplus.de, 
mail.discoplus.de,
www.discoplus.de

are subdomains. This allows multiple resources under the same domain. A subdomain may even be close to public. Like on a intranet.

For practical reasons nowadays most web servers are configured to redirect www.domain.com and domain.com to same place. So it may look like they are the same but in fact they are just separate addresses both pointing to a single address.

When you type https://wwwservice.discoplus.de/ you are being redirected probably becuase that URL doesnt exist you are redirected to a starting page.

The orther thing is the protocol.

when its http:// it refers to HyperText Transfer Protocol which is a standart protocol for web pages. if it has an "s" like https:// this means its secure* and the data being transferred is encrypted.

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A URL is composed of [Protocol][Domain][Folder and File Structure]

The part you're asking about is the domain part, ans domains have a few rules. But trying to keep it simple, the normal www in websites represents a particular machine (the web server) and is not mandatory, but its only supported if explicit in the DNS structure od the domain.

More info here

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