ELI5: What is the difference between correlation and causation?

Let's use Lego to understand correlation and causation.

Imagine you have a big box of Lego.

Correlation means you notice two things happening together often. For example:

• You see that when your Lego tower is really tall, it also has lots of blue Lego bricks.

But, does using blue bricks make the tower tall? Not necessarily! This is where causation comes in.

Causation means one thing actually makes the other thing happen.

Let's say you always put a special Lego Technic brick at the bottom of your tower. And every time you use that Technic brick, the tower stands up straight and doesn't fall over.

• The Technic brick causes the tower to be stable!

• Correlation is just noticing things happen together. Maybe you just like using blue bricks in tall towers. The blue bricks aren't making the tower tall.
• Causation is when one thing directly makes another thing happen. The Technic brick being at the bottom makes the tower more stable.