Electricity is the movement of electrons one way or another. The electron is a very small mass particle that is classified as a lepton, meaning that is has mass and has a spin quantum number of +/- 1/2.
An electron has a mass of 9.0166 x 10^-31 kg, making it about 1/1800 the mass of a proton, which is a hadron. Hadrons account for most of the mass in normal matter, as opposed to dark matter, the nature of which has not been elucidated nor ever proven, but that is for another series.
This series is concerned with the storage of electrical energy in the form of chemical energy, and converting the two into useful currents. Most of the electricity that we use is quite transient in nature, but that stored chemically in batteries is much longer lasting, if not as intense.