It is worth noting that positive charges have lines of forces moving out from them and negative charges have lines of forces entering them.for attraction of charges one charge must have force line leaving and the other entering, since they must be opp. Like charges will repel on the other side since both the charges will have the similar type of lines of forces and will not enter or leave the mutual system of charges at the same time. It is also worth mentioning that closer the lines of forces stronger is the charge. The force lines are much like the magnetic field lines but they exist indepenently.