Neutralization
Neutralization is the reaction between an acid and a base that produces water and a salt, canceling the properties of both and moving the pH toward 7.
Definition
Neutralization is a double replacement reaction in which an acid and a base react to form water and an ionic compound called a salt, with the hydrogen ions from the acid combining with the hydroxide ions from the base to make water while the leftover ions form the salt, releasing heat as the amounts are matched and the solution becomes neutral. In aqueous strong acid-strong base reactions the net ionic equation reduces simply to $H^+ + OH^- \rightarrow H_2O$, with $\Delta H \approx -57\text{ kJ/mol}$, nearly the same value for any strong acid paired with any strong base, and in a titration the equivalence point is where moles of $H^+$ equal moles of $OH^-$, landing at pH $7$ for strong-strong pairs but shifting away from $7$ for weak acids or bases whose conjugates hydrolyze in water, so the resulting salt itself can end up neutral, acidic, or basic.
Example
Taking an antacid tablet for heartburn is neutralization in action, as the base in the tablet cancels the extra acid in your stomach; hydrochloric acid and sodium hydroxide react as $HCl + NaOH \rightarrow NaCl + H_2O$, sulfuric acid and potassium hydroxide as $H_2SO_4 + 2KOH \rightarrow K_2SO_4 + 2H_2O$, and farmers spread lime, a base, on acidic soil to neutralize it for crops. Titrating $25.0\text{ mL}$ of $HCl$ against $18.4\text{ mL}$ of $0.100\text{ M}$ $NaOH$ shows the acid contains $1.84 \times 10^{-3}\text{ mol}$ of $H^+$, a concentration of $0.0736\text{ M}$, while neutralizing acetic acid with $NaOH$ produces sodium acetate, whose acetate ion pulls protons from water and leaves the equivalence point basic, around pH $8.7$.
Key Insight
A bee sting is acidic and a wasp sting is basic, so a baking soda paste can soothe a bee sting while vinegar can help a wasp sting, since neutralization works equally well in both directions. Neutralization is not the same thing as reaching exactly pH $7$: buffers, the bicarbonate system in blood, and the carbonate in limestone that neutralizes acid rain all shift pH only partway rather than to a precise value, since the word really just means acid consuming base, not any particular final pH.