Who owns core root domains ?

[zk0185rg6id9]

I would like to have my own webpage. Let's say I would be able to have my own webserver, program and code my own webpage - why must I LEASE or RENT a domain and not be able to use my own ? For example I want to make it http://www.gtrfmb.ypd . Ypd is not registered anywhere and I am sure there are thousand of other combination I could come up with using 3 characters.

So my question is, who owns the rights to deny me to make my own domain under my own DOT XXX with my own website running on my own server with my own internet connection - or in essence, who gets to own the .coms or .ypds and get to lease/rent them out ?