Difference between OnClick() event and OnClickListener?

Question

I\'m always using onclick() event in most of my projects. But, I read about OnClickListener(). Can anyone tell what\'s the difference between these

Answer 1

We use

    public void button_onClick_name(View v)
{
-------
}

to define a method out of the class. But To define a component Click event within a class, we use onclick listener.