Care to share any excellent analogies that help you understand or explain difficult concepts?

This is a difficult question to phrase simply, but I’m looking for stories or links to metaphorical/allegorical explanations that have been extremely helpful to you. Perhaps it was one that gave you that “A-ha!” moment, or maybe one that you turn to when explaining something to others more clearly.

Examples:
The Monkeysphere
The Spoon Theory (pdf)

Both of these explain some aspect of the world in a really crystal-clear way. I’m looking for more links like these from any subject, perhaps ones that you turn to regularly as needed. Thank you.

Edited to fix link.