Natural and Unnatural?

I happen to see a blog where there is a mention about "un- natural" and i was trying hard to figure out the difference? i have never really understood why certain "things" in this world is unnatural while some are not...why some relations are unnatural and some are not...i am having a bad time with this differentiation...isnt it all a human made concept to degrade some and to upgrade others....whats wrong to some might be right for others....i wonder how this can be understood....as far as i am concerned....the most natural food in this world is Maggi which is unnatural to everyone else....