The passage of an electric current through a conducting solution or molten salt either is a type of Electrolyte that is decomposed in the process.

When a cathode, or negative electrode, and an anode, or positive electrode, are dipped into a solution, and a direct-current source is connected to the electrodes, the positive ions migrate to the negative electrode and the negative ions migrate to the positive electrode. At the negative electrode each positive ion gains an electron and becomes neutral; at the positive electrode each negative ion gives up an electron and becomes neutral.

The migration of the ions through the electrolyte constitutes the electric current flowing from one electrode to other.

Electrolysis is used in the commercial preparation of various substances, e.g., chlorine by the electrolysis of a solution of common salt, and hydrogen by the electrolysis of water. The electrolysis of metal salts is used for plating.