What does a weather vane do to indicate the direction of the wind?

A weather vane is a device that rotates freely on a vertical axis and is typically mounted on a high point, such as a rooftop. It is designed with an arrow or other indicator that points in the direction from which the wind is blowing. The wind pushes against the vane, causing it to rotate and align with the wind direction, allowing observers to easily determine which way the wind is coming from.