What is ionization; in relation to acids?

Consider the ionization of hydrochloric acid:

##HCl(aq) + H_2O(l) rightleftharpoons H_3O^(+) + Cl^-##

The charge separation that the acid undergoes upon protonolysis, i.e. its donation of a proton to the molecule, is the so-called ##"ionization."##

For stronger acids, ionization (and protonolysis) is almost complete, and the equilibrium lies strongly to the right.