Coulomb's low of inverse square states that force between two charges proportionally depend on the product of magnitude of charges and inversely dependent on the square of distance between those charges.
i.e.Fαq1q2&Fα1r2
⇒Fαq1q2r2
Substituting constant,
→F=Kq1q2r2
Now, Significance :- Product at both the charges implies that the force is dependent on both of charges not only one charge.
Also, r2 signifies about symmetry,i.e. in any direction, for ex . x=+S & x=−S will have some force. which is called Symmetry.