The document discusses Bronsted-Lowry acid-base theory, which defines acids as substances that can donate protons and bases as those that can accept protons. An acid-base reaction requires one reactant to donate a proton while another accepts it. Conjugate acid-base pairs are formed when a proton is transferred between two molecules, producing a conjugate acid and conjugate base. Examples are provided of identifying the acid, base, conjugate acid and conjugate base in reactions.