what is a smile

what's a smile, people say it's something on your face when you're happy, but is it really, when people ask me what is a smile I'll say, it's something where you hiding what's is going on in your life, you're hiding your tears, a smile is when you hide all of your emotions and putting them deep Down, it's called a fake smile,so people don't ams are you ok, what's wrong, so people think you're happy,so what is a smile