Water molecule has an oxygen atom that is covalently bound to two hydrogen atoms. Valence-Shell Electron Pair Repulsion Model (VSEPR) represents a method that is used to determine the geometry of a molecule. VSEPR method is based on the property of negatively charged electrons to repeal each other.
Since the shape of a molecule influences it's properties and reactivity, is important to determine what is the shape of water molecule. Hence, if the bond angle in water molecule is of 180^o, then the molecule is non-polar since there exists no positive or negative charges at the molecule ends. If the water molecule is V-shaped, then the top of the molecule is occupied by the hydrogen atoms and it is positively charged, the hydrogen atoms weakly attracting the shared electrons, and the bottom molecule is occupied by the oxygen atom, which is negatively charged.