There are several Galaxies in our universe, to many to even be counted (at least 100 billion), we have yet to go explore any other galaxies since the nearest Galaxy is 2.5 million light years away. Our galaxy is called the Milky Way.
Galaxies are made of dust, gas, and dark matter. they are all held together by gravity.
There are three main types of Galaxies; Spiral, Elliptical, and Irregular.
Spiral Galaxies- the name gives it away, the gas and dust gather into spiral. the are different types of Spiral Galaxies; sa, sb, sc. Sa are more tightly spiral, the milky way is type of sa. Sb are a little more loose than sa. Then sc is even more spread apart, it is the least tighten of the three. sa has the biggest nucleus, while sc has the smallest.
Elliptical Galaxies- they look like circular blobs of light. they can be on a range to 0 to 7, zero being looking like a circle to seven being more long and narrow. They are mainly made out of just old stars, and not much gas and dust.
Irregular Galaxy- they do not have a clear figure unlike the other two. These galaxies usually have more gas and dust, this makes the galaxy have more star formation, because of that the galaxies are very bright.
cool fact- in about 4.5 million years it's expected for the Milky Way and Andromdea to collide