A protoplanetary disk is a rotating disk of gas and dust surrounding a newly formed star. This disk is where planets, moons, and other celestial bodies begin to form. The material in the disk gradually clumps together due to gravity, leading to the creation of solid objects. As the star continues to evolve, the protoplanetary disk can develop into a solar system. The process involves complex interactions between the particles, which can lead to the formation of larger bodies like planets and asteroids. Understanding protoplanetary disks helps astronomers learn about the origins of solar systems like our own.