Stars. Massive gaseous bodies that radiate light derived from their internal sources. Only a very small percentage of the trillions of stars that make up the observable universe are visible with the naked eye. Several stars form pairs, multiple systems, or constellations. The members of such stellar groups have a common origin and are bound together by their mutual gravitational attraction. In some ways, star clusters and stellar associations are similar. Star clusters are loose groups of physically similar stars that lack the mass to remain together as a group. The sizes, energy, temperatures, masses, chemical compositions, and motions of stars are all discussed. We will take a look at different stars of our known universe.