What exactly is happiness, moods and states of the mind?

Buddha mentioned that happiness is the greatest wealth. When going through the TED Happiness Topic , The habits of happiness , Depression, the secret we share , The struggle of mental health , All kinds of minds , How does my brain work? , What makes you happy? , etc. this left me wondering what exactly is happiness, moods and metal states in a Buddhists perspective. So what exactly is happiness? How is it the greatest wealth? How can happiness analysed using the Suttas and the Abhidhamma? How can this be extended to analyzing all moods and states of the mind?