Happiness is that feeling that comes over you when you know life is good and you can't help but smile. It's the opposite of sadness. Happiness is a sense of well-being, joy, or contentment. When people are successful, or safe, or lucky, they feel happiness.
In order to be happy, I personally beleive that it is important to challenge ourselves to grow and happiness is not an ultimate goal it is a byproduct of our actions.