Take carbon tetrafluoride, $CF_4$; the $C-F$ bonds all show charge separation in that fluorine polarizes electron density towards itself (i.e. a $C-F$ bond is polar!). Nevertheless, if we take the vector sum of these individual bond dipoles, the indvidual vectors sum to zero.
The same reasoning applies to $"C"Cl_4$, carbon tetrachloride, and $CHCl_3$, chloroform. Carbon tetrachloride is a non-polar solvent in that the bond dipoles will sum to zero (they must, because of the molecular symmetry, tetrahedral with $109.5$$""^@$ bond angles. On the other hand, chloroform has a degree of molecular polarity and is thus a polar solvent, inasmuch as the individual bond dipoles DO NOT sum to zero, and there is a resultant molecular polarity.
So how to conclude? Two factors determine molecular polarity: (i) bond polarity (which can be assessed by the electronegativity difference between the bound atoms); and (ii) the VECTOR sum of the bond dipoles.
