Dear student,
Electronegativity is a measure of how well an atom in a molecule will  attract electrons from a bond. The higher an atom's electronegativity,  the better it is at attracting electrons from a bond and the more time  the electrons will want to spend on that atom.
To determine how polar a bond is, you need to look at the  electronegativities of the two bonded atoms. The difference in  electronegativity will indicate how polar the bond is:
If you have a large electronegativity difference then one atom (the one  with the higher electronegativity) will attract the electrons from the  bond more, so the electrons will spend a disproportionate amount of time  on that atom giving it a partial negative charge and the atom it's  bonded to a partial positive charge.
If you have a small electronegativity difference then neither atom will  be able to draw the electrons away from the bond that well and so the  bond will only be slightly polar or not polar at all if the  electronegativities are the same.
 






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