If you mix an equal amount of acid and base, you get a material that is neither. Acids are neutralized by a base, so you get a neutral pH. Water and a salt are formed.

eg; NaOH+HCl--NaCl+H20

On the other hand, if you mix a strong acid and a weak base, the end product would be acidic. If you mix a weak acid and a strong base, the end product would be basic.