Open clusters are groups of stars that formed from the same giant molecular cloud and are held together by mutual gravitational attraction. They usually contain a few hundred to a few thousand stars and are relatively young in age, ranging from a few million to a few hundred million years old. These clusters are important for studying stellar evolution, as all the stars within them are roughly the same age and composition, providing a valuable opportunity to investigate how stars evolve over time. Open clusters are also used to study the structure and dynamics of our galaxy, as their distance and distribution can provide insights into the Milky Way's overall structure. Open clusters are typically found in the disk of a galaxy like the Milky Way, as opposed to globular clusters that are found in the galactic halo. They are often used as calibrators for measuring distances in astronomy and serve as benchmarks for understanding the properties and behavior of stars.