@Felix123 are you referring to DNS? or name servers?
Simply put, all webpages are hosted on an internet protocol address or ip address.
Something like 145.123.111.120
and rather than remember that string of numbers each time you want to visit a website we connect or map a name or domain name to that ip address.
Domain Name System tells the domain name where to point and map to that ip address that hosts the web files.
So when you type in example.com in a browser it redirects to the location of the hosted webfiles on 145.123.111.120