Electrostatic discharge, or ESD, is the sudden and momentary discharge of electric current that flows between two objects of differing electric potential. The term is usually used in the electronics industry to describe momentary unwanted currents that cause damage to electrical equipment.
ESD is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide. Either of these materials can suffer permanent damage when subjected to high voltage. As a result, there are now a number of antistatic devices that help prevent static build-up.
Another practical application of ESD knowledge is the use of lightning rods and ground wires in the modern housing industry. Lightning will discharge to anything that completes the shortest path on it's journey to the ground; often, that connector is a home. A properly place lightning rod connected to a wiring system that leads to a ground rod firmly planted in the Earth helps insure the home will not be damaged by the flow of the current.