What are the extension .gov .edu .mil and .net called?

The extensions .gov, .edu, .mil, and .net are known as top-level domains (TLDs). They categorize different types of organizations and entities on the internet, with .gov reserved for government entities, .edu for educational institutions, .mil for military organizations, and .net originally intended for network providers. These TLDs help users identify the nature and legitimacy of the websites they visit.