Answer:
Many hear me, but no one sees me, and I only speak when spoken to
I open wide and tight I shut, Sharp am I and paper-cut fingers too, so do take care, I'm good and bad, so best beware.
What is the thing which, once poured out, cannot be gathered again?
What flies forever, Rests never?
What is bought by the yard by is worn by the foot?
What covers its face with its hands, speaks no language, yet most known what it's saying?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?