Kw and what is its value? what will the [H+] x [OH-] equal? what is the pH scale? what do the numbers means? is a solution with pH 8 and acid or base?...

Water- how is it both acid and base? what is Kw and what is its value? what will the [H+] x [OH-] equal? what is the pH scale? what do the numbers means? is a solution with pH 8 and acid or base? what about a 3? what does it measure? how many times more acidic is a 3 than a 4? what about a 3 compared to 6? what is pOH?