Scattered across the Universe are billions of galaxies which each contain millions of stars. They come in many different shapes and sizes such as:-
A Spiral galaxy is a spinning galaxy with long curved arms, which has young stars, pink nebulas and dust found in them.
A Barred galaxy has long trailing arms with a central bar which is where new stars form at the end of.
An Elliptical galaxy are rounded and are made up of older stars. Many of which are found in clusters, with what they call Black Holes in them. This means that the gravity is so strong that not even lights can escape, we can only see the hot gas, dust and stars getting pulled into it.
An Irregular galaxy has no recognisable shape hence the name. They are usually small with lots of young stars and bright nebulas in them.
The Whirlpool galaxy is a huge, well defined spiral galaxy which is about 31 million light years away. It has a smaller satellite galaxy seen surrounding it and these are thought to contain super massive black holes within them.
To finish off, although most galaxies are light years away from each other, sometimes they do collide, and this is thought to have occurred mainly with Elliptical galaxies.
During collisions, clouds of gas between the stars are forced together, triggering the birth of new stars, and one of the best known examples of this is the Antennae galaxies.