Domain Name System

Laziness led to Domain = D here.

It's not just 1 system that caches all the millions of sites, something deeper.
It consists of 3 servers:

So, the Auth servers (3rd) store the Ds with their IP addresses. The text instructions to determine the IP address for a specific D are DNS records or zone files.

Let's see some!

1. A | AAAA : resolve D to IPv4 | IPv6
2. PTR : reverse of 1, check email spams
3. CNAME : aka another domain (when typing www.instagram.com, it leads to instagram.com)
4. MX : the server to send email to
5. NS : name of auth server
6. SRV : get service and port number
7. TXT : text info about D