When I’m first said, I’m quite mysterious, but when I’m explained, I’m nothing serious. What am I?

Answer: A Riddle!

More What am I ? with answers

More What am I ?

When it comes to me, you go on red and stops on green. What am I?
When people can control me, people love me. When people lose control of me, people fear me. I cast shadows, but have no shadow myself. What am I?
When set loose, I fly away. Never so cursed, as when I go astray. What am I?
When you are inside me, you will be encouraged to slam other cars. What am I?
When you do not know what I am, then I am something. But when you know what I am, then I am nothing. What am I?
When you have me, you feel like sharing me. But, if you do share me, you don't have me. What am I?
When you take away the whole from me, there is always some left. What am I?
Where force can't get through, I with a gentle movement do. What am I?
Where there is light is the only place I can live. Yet if light shines on me I die. What am I?
While I'm a challenge for one and a rebuke between two, Yet I still have a direction for every number. What am I?
White, dark, round, square, big or small, I am seen on Valentine’s Day, and loved by all. What am I?
Whoever made me don’t want me. Whoever bought me don’t need me. Whoever use me don’t know me. What am I?