The Earth revolves around the Sun because the Sun’s gravity pulls on the Earth, in order to keep it in orbit.
The Big Bang that occurred about 13.8 billion years ago had left the universe filled with dust and gas. Eventually, out of this dust and gas, the stars formed. The stars had a gravity center, due to which the remaining dust and gas started to be pulled towards them. The dust that was too far away to be pulled settled at a comfortable distance from the star.
About 4.54 billion years ago, our Solar System was just beginning to be formed. As our Sun was formed, and the dust and gas was settling around the Sun, a supernova nearby sent all the dust flying again. However, the force of a supernova with which the dust would have scattered would have been enormous. As the dust scattered, it started bumping into each other and started combining to form what would eventually become the planets, moons and asteroids.
According to the law of conservation of angular momentum, if no outside force acts on a moving object, then no change of angular momentum can occur. This is exactly what happened with the resulting planets, moons and asteroids. As they were already moving in the opposite direction of the supernova, they continued to move even after whole planets had formed. Their entire reason for moving is that nothing stopped them from moving.
Still, this does not explain why the planets and specifically Earth revolve around the Sun. As previously stated, stars have a very strong gravity center. So, while the planets were moving ahead, the Sun was pulling them closer. Eventually, the planets and the asteroids fell into orbit around the Sun, at a distance where the pull of the gravity of the Sun and the planet, and the speed of the planet’s movement balance out. Whereas, the moons fell into orbit around the planets.