DNS – Domain Name System – is a system that "converts" domain names into corresponding IP addresses.
The Internet works in such a way that it doesn’t recognize alphabet, but only numbers and every time you send a request for this or that domain name DNS service "translates" it into IP address. It is much easier for us to remember a domain name rather than 4 octets of numbers (for example, what would you remember faster namecheap.com or 74.81.78.44 - its IP address?).
And it is only 1 site. What if you need to visit 10 sites? You’ll have to remember!10 IP addresses, that is not very convenient. Here DNS comes for help.
It works in such a way: you send a request for a webpage >> a computer sends a request to the nearest DNS server, which finds the correct IP address (if not it sends a request to another DNS server, etc. until it finds the proper IP address) >> the computer connects to the server with this IP address. Once all these steps are performed you can see the content of the requested webpage.