Answer:
gravitational force and outward pressure
Step-by-step explanation:
The stars are very massive stellar objects, so they have a strong gravitational force, which drives the star to contract itself, but also in stars there are nuclear reactions such as fusion of hydrogen and other elements, that releases energy and creates a pressure from the center to the star exterior, an outward pressure that goes against the gravitational force. So when a star is stable these two forces exist in equilibrium or in balance, in which the star does not collapse by gravity or disintegrate by its outward pressure.