Answer:
If I have it, I don't share it. If I share it, I don't have it. What is it?
I have rivers without water. Forests without trees. Mountains without rocks. Towns without houses.
Until I am measured I am not known, Yet how you miss me when I have flown.
By Moon or by Sun, I shall be found. Yet I am undone, if there's no light around
A skin have I, more eyes than one. I can be very nice when I am done.
What did the piece of wood say when he saw the screwdriver and screws approaching?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?