The formation of water occurs by sharing of electrons between two hydrogen atoms and one oxygen atom. Covalent bond is present between the hydrogen and oxygen atoms. In water molecule, due to the electronegativity difference between hydrogen and oxygen; hydrogen get positive charge and oxygen get negative charge.
Thus, a molecule with positive and negative ends is said to be polar molecule. Due to its polar nature, water can bind to another water molecule and form hydrogen bonds. Water has also many unique properties due to its polarity such as it's ability to dissolve huge variety of chemical substances.
Thus, water has very unique properties that result from the fact that it is a polar molecule.