It takes about 365 days for us to orbit the sun. The same thing happens on Earth when we look at stars. That's because your left and right eyes look at the finger with slightly different angles. Then close your right eye, and look at the finger with your left. Look at it with your left eye only, closing your right eye.
For a simple example of parallax, hold up your index finger in front of your face at arm's length. Another reason that humans started to realize that we might not be the center of the universe came from looking at parallax, or apparent change in the position of the stars with respect to each other.
