How do ions behave in solution?
When ions are in solution, they have been pulled apart by the dissolving properties of water.
When salt (NaCl) dissolves in water, ions of sodium and chloride pull away from each other.
NaCl(s) -> NaCl(aq)
A good video on this topic can be viewed here:
One reason this concept is important is that many reactions take place between dissolved ions, for example the double replacement reactions which produce precipitates.