Here's why:

* Acids donate hydrogen ions (H+)

* Bases accept hydrogen ions (H+)

When an acid and base react, the hydrogen ions from the acid combine with hydroxide ions (OH-) from the base to form water (H2O). The remaining ions from the acid and base then combine to form a salt.

Example:

* Hydrochloric acid (HCl) (acid) + Sodium hydroxide (NaOH) (base) → Water (H2O) + Sodium chloride (NaCl) (salt)

This is a classic example of a neutralization reaction, where the acid and base react to form a neutral solution.