Generic TLDs

While .COM, .NET, and .ORG originally had charters (.COM was for commercial entities, .NET for network infrastructure, and .ORG for non-profit entities), those distinctions are largely blurred today and certainly not enforced in any meaningful way.

Today, these three are the big, incumbent gTLDs because domains under these namespaces are unrestricted and can be registered by any entity in any location for any reason.

There have been other TLDs over the years attempting to position themselves as gTLDs, prior to the advent of the New TLDs. These have been Country Code TLDs (ccTLDs) attempting to position themselves as gTLDs.

For example, .CO markets itself as ".CO means Company," but the reality is .CO TLD exists as the Country Code TLD for Colombia. .TV isn't really a TLD about television. It's the country code for the small island nation of Tuvalu. WS touts itself as .WS = Website, but it's actually the ccTLD of Western Samoa. The list goes on.