The current ARPA-Internet hosts.
This domain name arose from the historic development of the Internet, and its predecessor ARPANET. The use of ARPA as a Top Level Domain was only temporary, until its hosts selected some other domain.
This domain was originally intended for any kind of government office or agency. More recently a decision was taken to register only agencies of the US Federal government in this domain. State and local agencies are registered in the country domains, which were developed in the 1990s.
This domain was originally intended for all educational institutions. Many Universities, colleges, schools, educational service organizations, and educational consortia have registered here.
This domain is intended for commercial entities, that is companies. This domain has grown very large and there is concern about the administrative load and system performance if the current growth pattern is continued.
This domain is used by the US military.
This domain is intended as the miscellaneous TLD for organizations that didn't fit anywhere else. Some non- government organizations may fit here.
There actually never were any formal restrictions on .org registration. It always was designated the "other" category, for websites that didn't fit into the category other domain name, such as .com or .net. And of course, domains such as .edu and .gov were always off-limits to most.
As the Web grew in popularity, it just so happened that many non-profits and other "credible" organizations did choose to register .org domain names. This may be where the false notion of .org meaning credible began to develop. I don't think it was done maliciously. In fact, since so many genuine organizations were using .org domain names, it makes sense why this belief became so popular.
Of course, the real problem is that a lot of schools started teaching students that when evaluating online sources, looking for .org in the domain name was a method to determine if a website was credible. But this just isn't true! The presence of a .org does not automatically make a website more credible.
And even worse, I believe that teaching people to look for .org as a sign of credibility can be incredibly dangerous. Instead of teaching critical thinking skills to carefully evaluate a source, it falsely claims that there's an easy way to determine credibility.
Now, more than ever, it is critical that we teach everyone to think critically about the web content that they consume.
There are no hard and fast rules that will readily determine whether a website is credible. I think that teaching people that they can simply look for .org in the URL and immediately accept a website as credible can do more harm than good.
Instead, we should be providing everyone with the critical thinking tools they need to evaluate and assess sources themselves.
And that starts with simple things like this silly website.