Causation is the relationship between a cause and its effect: the connection between something happening and what it makes happen. When you push a domino and it knocks over the next one, that's causation. The first domino caused the second to fall.

Understanding causation means figuring out what really makes things happen. Things can occur at the same time without one causing the other. If you study hard and then ace your math test, the studying caused your success. But if you wore your lucky socks and aced the test, the socks didn't cause anything: that's just coincidence. Scientists spend enormous time and effort trying to establish causation, designing experiments that show one thing genuinely causes another rather than just appearing alongside it.

You'll often see this idea in the phrase correlation does not imply causation. This means that just because two things happen together doesn't mean one caused the other. Ice cream sales and drowning accidents both increase in summer, but ice cream doesn't cause drowning: hot weather causes both. Learning to distinguish real causation from mere correlation is one of the most valuable thinking skills you can develop, helping you understand how the world actually works rather than jumping to false conclusions.