What is Hubbles Law?

Hubble's law is considered the first observational basis for the expansion of the universe and today serves as one of the pieces of evidence most often cited in support of the Big Bang model. The motion of astronomical objects due solely to this expansion is known as the Hubble flow.

Explanation: Hubble was a person but they named a satellite that they sent out into outer space after him. He discovered that the galaxies that are the furthest away are moving the fastest away from us and the galaxies that are closer to us are moving at a slower rate.

So that is Hubble's law. Hubble's law is a mathematical thing that you can do if you take higher level astronomy. There is a mathematical relationship that you can figure out which is the the further away something is the faster it's moving away.