An extrinsic variable star is one that varies in brightness because of an external feature of the star.  There are two types of extrinsic variable starts: eclipsing binaries and rotating variables.

The first video is an example of an eclipsing binary system. The star varies in brightness when one star eclipses the other. When one star moves between the observer and the other star, less light is seen and the star appears to dim. No actual change in light output from the star occurs.

In the second animation, a binary companion causes the larger star of the pair to be pulled gravitationally into a non-spherical shape. The odd shaped star presents different amounts of surface area to the observer as it turns causing the star’s light output to seemingly change.