Domain Name Service (DNS) is a mapping of a domain name to an IP address, so that humans can remember computer address by a domain name instead of IP address. A DNS service is requested automatically when someone enters an web address on the web browser, so that the server knows how to find a website. When a user connects to the internet via a home router, the router gets an IP address and DNS server IP addresses via the DHCP it's Internet Service Provider (ISP). You may choose to use public DNS servers instead of the ones provided by your ISP by configuring your Internet connection manually.