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Suppose that a rubber balloon is rubbed with a sample of animal fur.During the rubbing process, the atoms of the rubber are forced into close proximity with the atoms of the animal fur.Rubber has a much greater attraction for electrons than animal fur. As a result, the atoms of rubber pull electrons from the atoms of animal fur, leaving both objects with an imbalance of charge. The rubber balloon has an excess of electrons and the animal fur has a shortage of electrons. 

Having an excess of electrons, the rubber balloon is charged negatively. Similarly, the shortage of electrons on the animal fur leaves it with a positive charge.Thus when any two objects are rubbed together, they become charged -one positively and the other negatively and so there will be attraction since unlike charges attract each other.