What is meant by quantisation of charges ?

Explanation

The force on a charge `q_(1)` exerted by a point charge `q_(2)` is given by
`vecF_(12)=(1)/(4piepsilon_(0))(q_(1)q_(2))/(r^(2) hatr_(21)`
Here `hatr_(21)` is unit vector from charge `q_(2)` to `q_(1)`
But `hatr_(21) =- -hatr_(12),`