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What is ww2/www2 in the URLs (2)

I have recently noticed some sites with URLs having ww2 or www2. What are they? Is there anything new that came up recently? Is there any link where I can get more information on that?

If you talk about things like www.example.com, ww2.example.com or somethingtotallydifferent.example.com. That is just a subdomain.

No one tells you how you have to name the servers in your zone, www is just a convention for a webserver.

This url's just shows that these websites are made using free web hosting sites or its just a subdomain.