confused about co.in co.uk co.whatever

I was wondering, if I would buy this domain name: http://www.co.in , could I create subdomains like: http://www.google.co.in ?
Yes I know google.co.in is already a registered domain name, but if you have your domain as: co.in you can create easily any subdomains like: google.co.in … etc
Could someone explain this a little more? If is possible or not?..

See original post by abyse