What you have learned at school is polar dissolves polar and nonpolar dissolves nonpolar, but why?
Water molecules are partially positive on the hydrogen and negative on the oxygen. These two atoms play an important part of dissolving NaCl.
In liquid, NaCl goes through dissociation, a reversible process that breaks the compound (NaCl) into ions (Na+ and Cl-). At this very moment, that is when partial negative charged Oxygen "captures" Na+ and partial positive charged Hydrogen captures Cl-
These water molecules essentially devour or dissolve these ions, not allowing them to form the compound, NaCl again. Therefore, NaCl is dissolved in water.
