when the force of gravity pulls large gas clouds and dust together, the concentrated gas clouds and dust collapse under the force of gravity forming stars.
There are many galaxies out there in the universe, each galaxy has its own solar systems, stars, and collection of gas and dust. We (earth) belong to the Milky Way galaxy, our galaxy got this name from the Romans. They called in 'via lactea', which directly translates to 'road of milk' because of the milky patch they saw at night.
