Acidity levels are different if it was a strong acid lets say lemon juice on the PH scale its close to two or three, but a weak acid like sea water is closer to eight so the difference between the two is one that has had water to it and the other is just weaker on the PH scale
In a dilute acid solution most if not all of the molecules will split into ions. For example HCl is a strong acid and 100% of the molecules will split into H+ & Cl-
in a weak acid solution only a portion of the molecules will turn into ions because the ionization percentage isn't as large. Which will essentially leave a high percentage of un-reacted molecules
