How is disk space used on macOS?

I just discovered a handy command-line tool to analyze disk space usage on macOS systems, and to answer the frequent question: where did my disk space go? All I need are two commands: first to install ncdu, and then to run it:

brew install ncdu
sudo ncdu -x /System/Volumes/Data

This command, combined with Apple menu → System Settings → General → Storage, solved most of my lingering questions on how my disk space is currently utilized.