how many galaxies are known
The best estimate from a 1999 study set that number at about 125 billion galaxies, but a 2013 study - after the Hubble Space Telescope was upgraded considerably - indicated that there are 225 billion galaxies in the observable universe.
There are three main types of galaxies: Elliptical, Spiral, and Irregular. Two of these three types are further divided and classified into a system that is now known the tuning fork diagram. When Hubble first created this diagram, he believed that this was an evolutionary sequence as well as a classification.