The Sun is not in equilibrium in the sense of being perfectly balanced by equal and opposite forces. Instead, it's in a state of hydrostatic equilibrium, which is a delicate balance between two opposing forces:

1. Gravity: The Sun's immense mass pulls inward on itself, trying to collapse it into a smaller, denser object.

2. Nuclear Fusion: The core of the Sun is a giant nuclear reactor, where hydrogen atoms fuse to form helium, releasing tremendous amounts of energy in the process. This energy outward pressure pushes against the inward pull of gravity.

This delicate balance is what keeps the Sun stable. The outward pressure from nuclear fusion precisely counteracts the inward pull of gravity, preventing the Sun from collapsing or exploding.

Here's a simplified analogy: Imagine a balloon. The air inside the balloon pushes outwards, similar to the outward pressure from nuclear fusion. The balloon's rubber stretches and pulls inwards, like the force of gravity on the Sun. The balloon is stable because the outward pressure of the air perfectly balances the inward pull of the rubber.

However, it's important to note that this equilibrium is not static. The Sun is constantly losing mass through the nuclear fusion process, which means gravity is slowly weakening. Over time, the Sun will need to adjust its fusion rate to maintain equilibrium, eventually becoming a red giant star.