The beginnings of the internet reach back to the 1960s.
At first it meant that computers talk to each other
by identifying themselves with numbers.
Every computer had a number known as an IP number,
and if you knew the computer’s number,
you could send it a message and someone on the other end would read it.
As the number of computers grew, this approach was considered impractical.
It's hard to remember such long numbers and who's who.
Then somehow the people who were developing the internet,
came up with the idea of using domains.
These are character strings, simple and familiar, such as
organisation names, surnames, first names, etc., and it’s easier to remember them
and also easier to access some interlocutors and sources on the internet.
And this is a domain system.
Once you have domains, computers still communicate
via numbers and thus you need
some sort of a system
to map these domains to numbers and vice versa.
And that’s called a DNS system.