What Song is in that Commercial? is a whole website to help you answer that very question.
explainshell.com uses some python and heuristics to show you the relevant manual text for a given command.
If this could be run locally on your own distro (rather than just Ubuntu) it would be a very powerful tool for beginners. As it is, it’s still pretty cool.
The OS X Recovery Partition: What It Is, Why It’s There and How to Remove It provides some great info about and tips. Among them, how to enable the Disk Utility debug menu.