You can think of Domain Name Server as a translator between human and machine language.
When you type a domain name into browser, the browser asks a Domain Name Server what IP the server behind that domain has. This is the most common record type known as A, but there are others that can provide more information like a location of mail server (MX), alias of domain (CNAME), protection (PTR, TXT), etc.

Location		resolve.	other local competition
		Average ping	Average ping
	Ljubljana	2.72 ms	6.41 ms
	Los Angeles	1.22 ms	167.71 ms
	Chicago	18.12 ms	127.8 ms
	Montreal	13.53 ms	126.48 ms
	Paris	12.71 ms	25.86 ms
	Amsterdam	1.36 ms	22.63 ms
	Nuremberg	5.67 ms	18.87 ms
	Milan	20.55 ms	19.18 ms
	Singapore	35.66 ms	280.16 ms
	Tokyo	2.25 ms	289.34 ms
	Sydney	111.66 ms	313.71 ms
	Qingdao	53.76 ms	307.41 ms

Tested with ping.pe