Answer:
I am lighter than the material I am made of. You see parts of me but more of me is hidden underneath.
I go up and down at the same time. Up towards to sky and down towards the ground
What has a head and a tail, but no body or legs?
When set loose I fly away. Never so cursed as when I go astray.
What is the difference between a poorly dressed man on a bike, and a well-dressed man on a unicycle?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.