Separation of biochemical moieties by electricity. It requires a medium, usually in the form of gel, to allow movement of the protein or nucleic acid. Some form of staining is required to render the gel visible.
The distance travelled depends on the molecular weight and charge of the molecule. A small, highly-charged molecule will travel further than a large, more neutral molecule. More complex separation techniques are possible combining a pH gradient in one direction and then electrophoresis in the perpendicular direction.