The early internet is just a few telephone lines with some router. It is only used by university anmilitary in United State. The mechanism is simple. Every computer terminal in the circus is assigned to series of ID numbers just like our ID cards.
If computer A wants to send a message to computer B then A must know B’s ID number and then send the information package to the routers and tell the routers to deliver to the computer with B’s ID number.
Right now we call the computer’s ID number to be IP addresses. For example, this is the ip address of www.google.com 157.166.266.25. As you can see, it is difficult to remember by human. Therefore some clever mind invented a DNS (Domain Name System).
The system is very simple. There are many DNS server it serves only one purpose that is translate a readable domain name to the IP address. The server stored a huge among of domain name -> IP address translation table.
How to trick your PC for domain name translation.
Besides the public DNS server, there every PC/Mobile phone has its own DNS table. It is usually a text file. When your PC/Mobile has found this table with the right domain name then it will not look further to the public DNS servers.