As with all sky objects, they can have several names. This particular cluster is identified by 3 names - the Pleiades, the Seven Sisters, and M45. The Pleiades (alias Seven Sisters, alias M45) is an asterism - not a constellation.

It's a group of young stars that shine brightly in the Winter sky. What makes this cluster so beautiful is that some of the stars are still surrounded by the stardust that they were originally formed from and as you can see, they reflect a beautiful blue color.