All matter is composed of atoms which are, in turn, composed of negative electrons and positive protons. These opposite charges attract each other and therefore require some effort to separate. Rubbing you feet on the carpet, combing your hair, passing a wire through a magnetic field, and many other processes can provide such effort. Once the charges are separated, they can be allowed to come back together in a controlled fashion and the energy used for some useful purpose such as lighting a lamp or toasting your bread.
