It is the phonebook of the internet (Converts Domain Names to IP Addresses)
DNS Working
Check Web Browser & OS Cache for IP Address
Send request to DNS Recursive Resolver (ISP) - Checks own Cache for IP Address
Send request to Root Server - Knows location to Top Level Domain (TLD) Server
Resolver is directed to TLD - Knows location of Authoritative Name Servers
Resolver is directed to Authoritative Name Server - Returns the IP Address of Domain
Resolver (ISP) caches the IP Address - Sends IP to requesting device
We can configure our devices to use a third-party DNS Resolver
If the Autoreactive Name Server returns a CNAME (alias) than the Resolver has to perform the whole process again for the alias