1. DNS
Domain Name Server. A type of computer on the internet that's something of a "master reference librarian" that keeps a list of all domain names and what computers they go to. Each DNS checks in with other DNS servers to find out what's new. A change in your DNS for your domain name takes 24 - 48 hours to travel all across the internet so that all computers know the new location to go to when someone types your domain name in a web browser.