DNS, or Domain Name System, is simply a database that links meaningful names (known as host names or domain names), such as http://www.microsoft.com, to a specific IP address, such as 192.168.124.1. This linking to a specific IP address is what allows your domain name and server to communicate, and as such for your website to display.
Nowadays the specific IP address you will need to use is already associated with a Nameserver(s). For example your nameservers will look something like: ns1.yourwebsite.com or ns2.yourwebsite.com. It’s these nameservers that are typically supplied to you by your host, that you will then use for your domain name. This is achieved by manually inputting the nameservers at your Domain Registrar (example: GoDaddy.com).
For further info on DNS check out this great briefing on it: The Internet Domain Name System Explained For Non-Experts