Answer : When atoms in a covalent bond share electrons unequally (one atoms pulls more than the other), the bond is said to be, Polar-bonds.
Explanation :
Polar bond : It is defined as the covalent bonds in which the electrons are shared unequally (that result in partial charges) between the elements that have different electronegativity. In the polar bond, the electron cloud is in distorted form. Polar bonds have a dipole moment.
For example : HCl, NaCl, etc.
Non-polar bond : It is defined as the covalent bonds in which the electrons are shared equally (that result no charges) between the elements that have same electronegativity. In the non-polar bond, the electron cloud is not in distorted form. Non-polar bonds don not have a dipole moment.
For example : 
Hence, when atoms in a covalent bond share electrons unequally (one atoms pulls more than the other), the bond is said to be, Polar-bonds.