One of the things that quickly became clear when I started teaching an introduction to computer science course for high school freshmen was that while they are happy to use the Internet, they don't really understand how the Internet works. I suppose the same can be said for lots of adults too. The Domain Name Systems is the most important or at least most frequently used part of how people use the Internet today. PowerCert Videos, a YouTube channel that I featured a couple of weeks ago, has a good video that explains how a DNS server works. I used this video with my own students earlier this year.
Code.org offers a video on the same topic. Code.org's video gets into a bit more of the history of the development of the Internet. I also showed this video to my students, but I didn't find it nearly as effective as the PowerCert video.
Applications for Education
If you have never built a website from scratch without the use of service like Weebly or Google Sites, you may not have ever thought about the role of IP addresses and the domain name system in getting a website online. These videos can help students understand how that process happens and how DNS makes it easy to navigate the web today.