Molten $\mathrm{NaCl}$ and a concentrated aqueous solution of $\mathrm{NaCl}$ are electrolysed separately using inert electrodes. The cathode products are respectively

In the melt only $\mathrm{Na}{}^{+}$ is available for reduction, so sodium metal forms at the cathode. In aqueous solution water is reduced in preference to $\mathrm{Na}{}^{+}$ because $E^{\circ }(\mathrm{Na}{}^{+}/\mathrm{Na})=-2.71\mathrm{V}$ is far more negative than the potential for $2\mathrm{H}{}_2\mathrm{O}+2\mathrm{e}{}^{-}\to \mathrm{H}{}_2+2\mathrm{OH}{}^{-}$. Hence $\mathrm{Na}$ from the melt and $\mathrm{H}{}_2$ from the aqueous solution.