When an ebonite rod is rubbed with wool, the ebonite rod acquires negative charge. When a glass rod is rubbed with silk, the glass rod acquires positive charge.
In fact when two substances are rubbed together, one acquires negative charge and the other acquires equal amount of positive charge.
Thus, there are two types of charges:
(i) Positive charge (ii) Negative charge
The names positive and negative charges were given arbitrarily.