When it all started years ago.
There was 7 specific domain suffixes
1 - .gov for Government agencies.
2 - .edu for official Educational organizations (like Universities).
3 - .mil for the Military.
4 - .int for International organizations.
5 -
.org for none for profit organizations (None for profit is a form of corporation the does not suppose to make any profits, and thus does not pay taxes).
You can Not get any of the above suffixes without being certified that you belong to one of the categories.
6 - .com that suppose to stand for commercial.
7 - .net for Networks
The last two became the general suffixes that any one can buy and did not actually have to be commercial or Network entity
Every body liked the .com so we are almost out of .com, .net is relatively available.
In order to provide for the whole world there are many more suffixes that are country specific as well as .info .biz .us and few more.
If you are Not officially incorporated as none for profit organization I doubt that you can obtain an .org.
You can not change the suffix since the suffixe is part of the domain.
Example:
http://www.new.com has nothing to do with
http://www.new.net
:sun: