Answer and Explanation:
Stars get born from dust and gases that are dispersed in the universe. All the stars differ in their mass and chemical composition, but generally speaking, they are formed by 70% of hydrogen, 24-26% of helium, 4-6% of chemical elements called metals.
Gravity is a force that plays an important role in star formation. It is in charge of getting together and comprising all the elements in the nebula, the dust, and gases. During the comprising process, these elements get heated, causing gradual and consequent heating in the core of the forming-star, which is called proto-star. In a proto-star, the core is not hot enough and gravity is still comprising elements from the molecular gas cloud of the interstellar medium. This makes the core to be more comprised and heated each time. When the amount of comprised material is big enough, the core reaches such an elevated temperature that it turns on a "nuclear oven" which is the highest pressure and temperature point in the star. At this point, the core starts to release important amounts of energy. The new star is in an equilibrium point, where gravitational forces that pull material to the interior of the star, are compensated by the gas and radiation pressure emitted by the star core that pulls matter out.
