A transformer is a machine that changes electrical voltage, making electricity stronger or weaker depending on what's needed. Power plants generate electricity at very high voltages to send it long distances through power lines. Those big gray cylinders you see on utility poles? Those are transformers, stepping down that high voltage to safer levels before the electricity enters homes and businesses. Without transformers, you couldn't plug in your devices safely because the voltage would be far too high.

You've probably also heard of Transformers, the fictional robots that can transform their bodies into vehicles or other shapes. That franchise borrowed the word because those characters literally change their physical form while remaining the same robot inside.