Question

What are internet domains?

Answer 1

If you do indeed mean internet domains (or Top-Level Domains), they are the suffixes usable by websites such as '.com', '.org', '.net', etc. These are controlled my ICANN and are simply different ways to let the user know perhaps a bit of info before they go to the site.

For Example, a .org generally means that it is owned by an organization. (Though the meanings for each are starting to slowly fall off.)

http://en.wikipedia.org/wiki/Top-level_domain