The state that exists when acidic and basic ions in solution exactly neutralize each other is called acid -base equilibrium.
Consider an acid, HA, in water. According to the Brønsted-Lowry acid/base theory, the acid should protonate the water to form hydronium and the conjugate base, A-. There will be an equilibrium between the acid and water, and hydronium and the conjugate base.
This equilibrium can be used to calculate the concentrations of species in the solution.