The Five Worlds

I knock at the door and a old woman opens the door. "Can I live there for one night?" I talk to this woman. Woman smiles and says: "No problem." then I walk into the villa. She then ask me to be seated and prepare some food for me. After about fifteen minutes, the woman gives me a bottle of water and some biscuits. I say "thanks" to her and I start to eat it. After I eat up all of the biscuits, I have a bad headache and I go unconscious. After a period of time, I wake up and I am tied to a chair. Woman is standing right in front of me and says "I will give you a riddle and you need to give me the answer. If the answer is correct, you can stay alive. But if the answer is incorrect, you will die." Then she gives me a paper and there is a riddle:

A thing can move without feet
Can talk without a mouth
It can give orders
And everyone needs to obey it
What is it?