Follow the idea
pH is a logarithmic way of expressing hydrogen-ion activity; introductory calculations often approximate activity using concentration in sufficiently dilute solutions. Because the scale is logarithmic, a change of one pH unit corresponds to a tenfold change in the relevant hydrogen-ion activity ratio. At chemical equilibrium, forward and reverse processes continue but their rates are equal, so macroscopic composition no longer changes with time. Equilibrium is dynamic, not a frozen reaction. That single idea prevents one of the most common misunderstandings in chemistry. An ion is an atom or molecular entity carrying a net electric charge because its numbers of protons and electrons are not balanced. Losing electrons gives a positive charge; gaining electrons gives a negative charge. This simple bookkeeping is behind salts, electrochemistry and much of solution chemistry.
Primary references
IUPAC Gold Book · NIST · BIPM