I'm under the impression that the word belief means, something believed or accepted as true by a person.
You may accept something as being true from personal experience or thorough understanding of the subject matter, or you may accept it as true because you have faith in the person that expresses it as being true.

Suppose that you have never studied astronomy and a professional astronomer says that there is NO ice or atmosphere on the moon.
Then you meet a friend of yours who's hobby is astronomy, and he says that there IS ice and an atmosphere on the moon.

Would you believe your friend or the astronomer?

I'm a curious person and would ask why they believe in what they are saying.
If I would believe either persons assertions without question, then I would have faith in that persons ability to interpret the conditions on the moon.
Having faith in a subject without questioning or understanding the subject matter seems to me like a "belief system".

Johannes