[Wayback/Archive] mess with dns: a cool site at messwithdns.net
that allows you directly mess around with subdomains of messwithdns.com
(yup: these are on different top level domains by intent, see [Wayback/Archive] mess with dns: about/FAQ).
Her blog post [Wayback/Archive] New tool: Mess with DNS! has a cool insightful explanation with lots of gifs showing what is going on. The below gif is just one of them:
In addition, it has a cool [Wayback/Archive] mess with dns: DNS dictionary explaining common DNS related terms.
The backend is written in Go, and has a snapshot of the initial source code on github at [Wayback/Archive] jvns/mess-with-dns-backend (mainly so you can file issues or submit ideas).
Oh, and this is a cool video that shows you how DNS works assuming the protocol is phone based: [Archive] Max Meier👨🏻💻🛡⚔️ on Twitter: “DNS Server …” / Twitter.