A directed acyclic graph (DAG) is a picture of causal assumptions. Each node is a variable; each arrow means “this may cause that.” Drag from one node to another to draw an arrow.
Drag from one node to the other to show which variable you think causes the other.
Draw arrows among all three nodes. Try a mediator chain (Smoking → Inflammation → Cancer), then clear and try pointing both Smoking and Cancer into Inflammation, or both arrows out of Inflammation.
Takeaway: The same variables can be arranged into different causal stories. A mediator lies on the pathway; a confounder affects both exposure and outcome; a collider is where two arrows meet.