When two materials are rubbed together, electrons may be transferred from one to another, for example, when a polythene rod is rubbed with a dry cloth, the cloth will lose electrons and the polythene will gain electrons, so the electrons will be transferred from the dry cloth to the polythene, with and a positive charge appearing on the cloth and a negative charge appearing on the polythene. Rubbing materials together does not of itself make charges, but simply creates negative and positive charges which already exist within the materials.