I don't understand philosophy...What is philosophy ?

Hi,

I think that my title describes what I'm asking for. What exactly is philosophy and what are its goals ? I did take some classes on philosophy and I did pass all of them, but if someone were to ask me what is philosophy, I seriously wouldn't know what to say. On the contrary, if someone were to ask me what is natural science, I would easily be able to respond to him.

COuld someone explain to me, in simple terms, what is philosophy? Thank you!