OH- is hydroxide, a BASE > proton acceptor > produce hydroxide ions when dissolved in solution H3O+ is hydronium, an ACID > proton (H+) donor > produce hydrogen ions when dissolved in solution
For more BASIC solutions: concentration of BASE> con. of ACID con. OH- > con. H3O+
The concentration of H3O+ must be less than or SMALLER than 1x10^-7 (so 1x10^-8, 1x10^-9 etc.) whereas the concentration of the base, OH-, must be LARGER than 1x10^-7. So there is a higher concentration of OH-, or more mol OH per L of solution.
pH measure the concentration of H+ or H3O+ ions in solution. It is -log[H+] ... so if the concentration was lower than 1x10^-7 mol/ L -log(1x10^-8)= pH= 8 which is Basic (x>7)
Remember, for the pH scale, (0-7)= acidic 7= neutral (7-14)= basic
Conversely, for acidic solutions, the concentration of hydronium would increase
