TLD = Top Level Domain (the thing at the end of a Domain (.com, .us))
ICANN = The Organization who manages all of this and makes the Rules.
I have several Issues with the ICANN and their decisions they made about Domains and what are and aren't TLDs. Like they had a great Idea with making .edu, .com, .net, .org and .gov for Defining the purpose of Sites. Also having Countries TLDs based on the Country codes .us .de .it .tv etc. wasn't bad either, maybe combining them with purpose driven TLDs similar how the UK manages their with co.uk, org.uk would have been a good Idea. But then they opened all of them for everything completely eliminating the meaning of a TLD. And then they made the Registering your own TLD and option for the big Companies. Which just why. What's the purpose of a TLD now. Except being an unnecessary, meaningless extension at the end of my Website.
Also, there other things the ICANN has done that makes me a bit mad at them.