What does the polar nature of water molecules have to do with substances being able to dissolve in water

Water is only able to dissolve polar molecules and ions. This is because, for a substance to dissolves in water, it has to positively interact with the water molecules (that have partial positive and negative charges). H-bond will form between the partially positive hydrogen ends of water molecules and the negatively-charged ends of the dissolved molecules. The partially negative oxygen ends of the water molecules, on the other hand, interact with the positively-charged ends of the dissolved molecules.

Molecules with no charge are hydrophobic.