Domain/Subdomain vs DNS, NIC vs Registrar

Some IT beginners may get confused between domain and subdomain, by thinking more than 1 dot is subdomain but thats wrong.

Domain goes with extension, extension is managed by NIC, aka network info centre.

Domain is resolved by DNS (domain name system), in which DNS (domain name server) is, DN servers are managed by registrar.

Subdomain is the part after domain, subdomain is managed by registrar. Domain may come with 1 or 2 dots. Eg foo.com, foo.com.vn.