CCl4 is a non-polar molecule. The four C-Cl bonds are polar, but they are arranged in a tetrahedral geometry, which results in a non-polar molecule.
Polarity arises from a difference in electronegativity. The chlorine molecule is more electronegative than the carbon and attracts the bonding electrons more strongly. The uneven distribution of electrons in the C-Cl bond makes it polar, with the chlorine being negative.
The four bonds are arranged around the carbon like the legs and neck of a camera tripod. This is called tetrahedral geometry. The four polar bonds in this geometry negate each other's effects, resulting in a non-polar molecule.