The generic ionic solid is $MX$, and consists of equal number of $M^+$ and $X^-$ ions that are held together in a non-molecular, electrostatically bound lattice. The ions are not free to move in the solid state, and thus cannot carry a charge.
In certain circumstances, with certain solvents, for instance water, the ionic solid can dissolve to produce $M^(+)(aq)$ and $X^(-)(aq)$ ions that are free to move in solution. We write $M^(+)(aq)$ to represent the aquated ion, i.e. $[M(OH_2)_6]^+$ or something similar. And in solution these ions can carry a charge in that the ions are mobile.
Water is an excellent for solvating ions. However, it does not solvate all ions, and it is not the only solvent available.
