Galaxy is a term that originates from the word gala, which means "milk" in Greek. Initially, it was the name of our galaxy, the Milky Way, and then generalized as a denomination of all others.
The galaxies are composed of gas clouds and dust, a large number of stars, planets, comets and asteroids and various celestial bodies united by the action of gravitational force.
On a starry night, we can see a whitish strip that cuts through the sky. This "band" of stars is just part of the galaxy where planet Earth is located. The ancients called it Milky Way, whose Latin meaning is "milk path".
The Milky Way belongs to a cluster, ie a cluster of several galaxies. The universe contains more than 200 billion galaxies of varying size and shape. There are galaxies of elliptical form, others are spiral and many are irregular galaxies, that is, it has no specific shape.
Representation of the Andromeda Galaxy
Milky Way Representation profile view (above) and top view (below)