The domain name system (DNS) is an area that confuses almost everyone.
How the hell does it work? What are A-records, CNAMEs, nameservers etc.!?
I did a detailed breakdown of this for the 6 Week AMC, including a huge schematic.
If you watch this and understand it, you should have a decent grasp on DNS.
Why would you want to know about this? Well, if you are managing your own self-hosted software its useful to have at least a basic understanding of the systems in play, how they are involved and how they can affect your campaigns right?