angular momentum - What causes precession or nutation in a spinning object?

1. 
   

   What causes precession in a spinning object?

   
   


2. 
   
   

   What causes nutation in a spinning object?

   
   


3. 
   

   What causes a top, gyroscope, and the earth to wobble?

   
   

Just because it's a simple question, I'm not expecting a simple answer, but please do summarize whatever you say in laymen terms, thanks.