A polar molecule does not have an even distribution of electrons. The electrical charges are not evenly distributed, causing one end to be more charged than the other.
A non-polar molecule has an even distribution of electrons. Since the electrical charges are evenly distributed, they cancel each other out.
Chloroform can be written as CHCl3.
Therefore the Lewis Structure of Chloroform is:
As you can see, there are four bonds in CHCl3 but two different bonds: C-H and C-Cl
Finding the electronegativity value of each atom in the bond can help determine the energy flow and whether a molecule is polar or non-polar.
|(green = Cl, black = C, white = H)|
C - 2.5
H - 2.2
Cl - 3.2
In the picture below, the arrows represent the energy flow of each bond, for it goes from lower value to higher value.
So the arrow goes from H (2.2) to C (2.5)
and from C (2.5) to Cl (3.2)
If the arrows all point to the same central atom, or if the arrows cancel each other out, then the molecule is non-polar, if not, than the molecule is polar.