How are Kepler's Laws important to astronomy?
Keplers laws describe how a celestial body behaves when it orbits something massive.
Kepler's laws describe how planets (and asteroids and comets) orbit the sun. They can also be used to describe how moons orbit around a planet.
But, they do not just apply to our solar system --- they can be used to describe the orbits of any exoplanet around any star. With some modifications, they can be used to describe how binary stars orbit around each other, how stars orbit a black hole, or how a white dwarf orbits around a neutron star. They can also be used to describe how (some) gas disks orbit around a star or black hole.