How simple and inadequate this definition is of a phenomenon that creates problems which cost industry millions of dollars per year. A clearer understanding can be gained by explaining lightning. Static electricity in the atmosphere remains at rest until the potential gradient, between clouds, reaches a level that causes the insulator between clouds, in this case air, to break down or fail, and lightning is created to equalize the potential gradient. For the brief instant the lightning flashes, the static electricity is no longer at rest. Well, let's examine it.
All matter is composed of atoms.
A balanced atom contains positive charges that are present in the nucleus of the atom. An equal amount of negative charges orbits this nucleus in the form of electrons. Both charges are equal and, therefore, the overall charge of a balanced atom is zero. However, should this configuration be disturbed and several electrons removed from this atom, we end up with a greater positive charge in the nucleus and a deficiency of electrons, which gives you an overall charge in the positive direction. Conversely, should we add a few extra electrons, we have an overall charge of negative, due to the fact that we now have an excess of electrons and the net charge is now in the negative direction.