A galaxy is a large collection of objects such as star systems, gas clouds and other celestial objects that are kept together by the action of gravity.
There are three main types of galaxies:
- Spiral, with radiating arms
- elliptical, a regular flattened sphere
- irregular, a collection without any regular pattern
Our Solar System is a member of a spiral galaxy called the Milky Way
The Milky Way courtesy of the ESA - Hi Res image here