What does it mean to say that angular momentum is conserved?

Give an example you might see on Earth. How could conservation of angular momentum help astronomers understand the development of the solar system? (this the part of the question that I don't understand)

2 answers

The solar system was formed when a gas cloud collapsed under its gravity. The initial angular momentum caused the cloud to collaps into a disk.
So what does this have to do with helping astronomers understand the development of the solar system? When the Earth rotates on its axis, is this part of angular momentum being conserved? Does angular momentum show the astronomers how the earth and other planets rotate?