Suppose if we have two charged bodies one is positively charged and one is negatively charged, then they will attract each other if they are kept at a certain distance from each other. Now if we increase the charge of one body keeping the other unchanged, the attraction force is obviously increased.
Similarly, if we increase the charge of the second body keeping the first one unchanged, the attraction force between them is again increased. Hence, the force between the charged bodies is proportional to the charge of either body or both.
Now, by keeping their charge fixed at Q1 and Q2 if you bring them nearer to each other the force between them increases and if you take them away from each other the force acting between them decreases.
If the distance between the two charge bodies is d, it can be proved that the force acting on them is inversely proportional to d2.
This development of force between two same charged bodies is not the same in all mediums. As we discussed in the above formulas, εr would change for various medium. So, depends on the medium, creation of force can be varied.
