Explain the Difference Between Correlation and Causation in Plain English

You have heard that correlation does not equal causation. What you might not have is a clear way to spot when someone is treating one as the other in an argument or a news headline. This explains the distinction without statistics, gives a concrete example, and leaves you with one question to ask when someone is claiming a cause.

Explain the difference between correlation and causation to someone who has heard the saying but does not understand when it actually matters.

Cover:
1. What each term means in one clear sentence
2. A concrete example of two things that are correlated but not causally linked
3. Why it is difficult to establish causation and what makes randomised trials different from observational studies
4. A situation where treating correlation as causation leads to a bad decision in daily life
5. One simple question to ask when someone claims 'X causes Y'

No equations. No statistics jargon. Under 200 words.