Then the Harmonic becomes the Prime and produces a harmonic, and so on. Thus the basis and roots for our music culture. They are not, but what are a few cycles amongst friends. That is why our scales are considered tempered. Sharps are used to indicate a tone that is raised step.
Flats indicate a tone that is lowered step.
But the real reason they are called sharps and flats is a matter of convenience. But that also would be confusing. If they did not use Sharps and Flats the logical flow of note names would become a horror. Anyway, hats off to the Monks, the wine, and the wonderful system they conceived. Imagine trying to learn that stuff 800 years ago.