Electrostatic discharge is the build-up of electrostatic energy on one object that is discharged onto another object. A good example would be a person walking across a carpet. As the person moves across the carpet, electrostatic energy is being built up. This energy can be passed to electrical equipment by a simple touch, sometimes resulting in damage to the equipment.
There are a few things that you can do to prevent electrostatic discharge (ESD).

1. Don’t place the PC on any carpet. Walking on carpet creates electrostatic discharge. This discharge is strong enough to damage any electrical equipment. Use a Surge protector. This device suppresses voltage spikes in the line that go above a specific threshold and protects electrical devices from voltage spike damage.
2. Use an ESD mat under the computer desk. Walking on carpet can still carry a charge through the human body. When touching an electrical device after holding a charge, the touch transfers (discharges) the charge to the electrical equipment. This charge could damage the equipment.
3. Ensure all equipment that is plugged into an outlet or power source is grounded. Having a ground wire helps to direct the flow of energy safely away from parts and persons!

For more information on Electrostatic Discharge, visit Wikipedia.