Planetary motion

Question: Why do planets revolve around the sun and why do they spin?

Answer:

It's all to do with how the Solar System was formed.
There was a huge spinning disc of gas and dust revolving around a star, our Sun. Very slowly particles came together in groups and as these groups grew they attracted more and more matter. These balls of matter eventually formed the planets. The original spinning motion was retained by the new planets and so they not only orbited the Sun but also continued to spin about their own axis.
So the spin is there because the original, disc was spinning.