What does "// TODO Auto Generated method stub" mean?

It means that your IDE (or some other tool) has automatically generated a method for you, but has left the body blank to be filled in by you (this is known as a "stub").

In your case, it was probably Eclipse.

This is a comment that's added by Eclipse (an IDE) when you have eclipse create a method body for you. It's meant as a reminder for the programmer that he/she needs to code something in the method