DNS stands for Domain Name Server.
It is like the phonebook for the internet. Getting around the internet requires that computers convert friendly names like google.com to whatever number is assigned to google.com. No one expects you to remember those, so DNS looks them up for you.
Most people use the DNS server assigned to them by their Internet Service Provider. This is usually automatic. But there is no rule that says you have to.
No matter what type of internet activity you are doing, you generate DNS lookups. Some DNS server somewhere sees every website you visit. That means a record is kept of your habits and activity that can be immediately identified as coming from you.
We recommend Quad9 and here's why:
Quad9 does not store any information about your activity. Additionally, they actively block malicious sites to provide a layer of protection against ransomware, phishing, and other types of malware.
You can visit Quad9 and the other optional DNS websites to learn more here:
Google DNS: https://dns.google.com