An electrolyte is a substance that produces ions in solution, which is evidenced by the fact that the solution is electrically conductive.

Due to the long-range intermolecular forces between ions in the solution, the use of activity coefficients when treating electrolyte solutions is essential, even for very dilute solutions.

Let the electrolyte be:

\begin{equation} M{\nu_{+}}X_{\nu_{-}}(s) \rightarrow \nu_{+}M_{ac}^{Z_{+}}+\nu_{ -}X_{ac}^{Z_{-}} \end{equation}

Let's compare this equation with the dissociation of barium nitrate. \begin{equation} Ba(NO_3)_2 \rightarrow Ba_{ac}^{2+}+2NO_{3}^{-} \end{equation} Where $M=Ba, X=NO_3, \nu_{+} =1, \nu_{-}=2, Z_{+}=+2, Z_{-}=-1$

Some dissolved ions can rejoin to form ion pairs.

\begin{equation} Z_{ac}^{Z_{+}}+X_{ac}^{Z_{-}}\rightleftharpoons MX_{ac}^{Z_{+}+Z_{-}} \end{equation}

To better see the formation of an ion pair, I give an example with barium nitrate in solution

\begin{equation} Ba^{2+}+NO_{3}^{-}\rightleftharpoons Ba(NO_3)^{+ } \end{equation}