If you direct Firefox (Safari, whatever) to a website, it needs to discover the IP address of the site. That will cause Firefox to generate an outbound call to a DNS server on port 53 (domain).
Various DNS servers are available. IP 8.8.8.8 is Google public DNS, and 208.67.222.222 is Open DNS. Many companies (like Google, Apple, M'soft) will also host DNS operations on Akamai, so you might get bounced around in an attempt to find servers that are geographically close to your location for faster connection speeds.
Various DNS servers are available. IP 8.8.8.8 is Google public DNS, and 208.67.222.222 is Open DNS. Many companies (like Google, Apple, M'soft) will also host DNS operations on Akamai, so you might get bounced around in an attempt to find servers that are geographically close to your location for faster connection speeds.