DNS stands for Domain Name System. It was invented because it is very difficult for us humans to remember long IP addresses when connecting to other servers on the Internet. Could you imagine having to write “34.218.145.143/home” in your internet browser instead of http://www.disneyplus.com ? no way ! In a nutshell, DNS is the system that gives you the answer to a question: What is the IP address of a given domain name?
So, there was the necessity of an easier way and that was through words and names as we already use them for communication and we are used to remember them. These names as referred as domains too. Once designed and it became public it was so useful that it quickly got a wide adoption and became a standard which is still used nowadays.
There are thousands, if not millions of DNS servers out in the world that merely help all the network capable devices (computers, phones, etc) on the internet to find out which IP address they should connect to.
When you configure your phone for example, you have the option of manually specifying an specific DNS server as your primary and secondary servers. Otherwise it is automatically taken from the DHCP response given by your wifi access point, or from your cellular/data provider if using your SIM card.
Be careful, an untrusted DNS server could redirect you to malicious servers. So you want to always stick to well known DNS server providers. Changing your default DNS server is not something you want to change unless you understand all the consequences it could come with. Check the post What could happen if I change my DNS server address? if you are curious.
In order to find out the IP address of a domain hostname like http://www.netflix.com for example, the Operating System on which the application is running will have to make a DNS query to the default configured DNS server. That DNS server will reply with the IP address and let your application connect through TCP/IP.
Still want to learn more? check the following posts.
What could happen if I change my DNS server address?
Which are some trusted DNS servers?
Luis Castro's Blogs 
One thought on “What is a DNS?”