DNS

The internet's phone book. It translates domain names (richgirlsystems.com) into IP addresses (the actual server location) so browsers can find your website.

DNS changes take time to propagate (up to 48 hours). Understanding it prevents panic when a website "disappears" after moving hosts, and helps you troubleshoot email deliverability issues.

A founder moves her site to a new host. She updates the DNS records at her registrar, and her site resolves to the new server within 4 hours as the change propagates globally.