A movement of electrons: An electric current consists of charged particles moving through a conductor usually consisting of electrons.

The electrons in some atoms; such as, copper and aluminum, are free to move and to jump from one atom to another and such materials are known as "conductors".

Other materials, such as wood, do not contain as many moving electrons, and so they are called "insulators", and when a material is neither completely a conductor nor an insulator, it is called a "semiconductor".

When an electric current moves continuously in one direction, it is called a "direct current", and when the current fluctuates rapidly back and forth, it is called an "alternating current".

Alternating current is used in almost all worldwide household wiring today while direct current is commonly seen in battery-operated devices.