RePublicDNS is a simple website that collect and check Public DNS Server worldwide
What is a Public DNS Server?
A Public DNS Server is one that has a lot of information about which website is hosted on which IP. When DNS resolves a website to an IP address it might have to ask multiple servers. The Public DNS Servers keep information about which other servers down the lane needs to be asked.
Your computer uses a Public DNS Server (if your ISP does not interfere with this) to assist you with opening your favorite websites. Using a Public DNS Server is reliable and highly encouraged as it will also speed up (to a minor degree) your browsing experience.