Simple acid/base question?

pH is a measure of the concentration of free H+ ions in solution. Acetic acid is a weak acid, which means that at any given moment, only a small percentage of its molecules are ionized, so there is a low concentration of free H+ ions in the solution. HCl is a very strong acid, meaning that almost all of its molecules are ionized at any given moment, resulting in a high concentration of free H+ ions in solution. And a high H+ concentration = a low pH.