There are many different types of variable stars, each with its own reason for changing brightness. Here are a few examples:

* Cepheid variables: These stars pulsate, expanding and contracting in a regular cycle. Their brightness changes in a predictable way, and the period of pulsation is directly related to their absolute magnitude (intrinsic brightness). This makes them incredibly useful for determining distances in space.

* RR Lyrae variables: Similar to Cepheid variables, these stars pulsate and have a clear relationship between pulsation period and absolute magnitude. They are often found in globular clusters.

* Eruptive variables: These stars experience sudden outbursts of energy, causing their brightness to increase dramatically for a period of time. Examples include novae and supernovae.

* Eclipsing binary stars: These are two stars orbiting each other, where one star periodically passes in front of the other from our viewpoint. The eclipse causes a dip in brightness.

* Rotating variables: Some stars have spots or patches on their surface that are cooler or hotter than the rest of the star. As the star rotates, these spots can cause its brightness to vary.

Understanding variable stars helps astronomers study stellar evolution, determine distances, and unravel the mysteries of the universe.