Electro Static Discharge (ESD) is the transfer of an electrostatic charge between two objects. This is a very rapid event that happens when two objects with different electrical potentials come into direct contact with each other. This charging results in one object gaining electrons on its surface area to become negatively charged, whilst the other object loses electrons from its surface area and therefore becomes positively charged. The creation of an electrical discharge by this contact and separation of objects is known as triboelectrical charging, which also explains the small static electric shock you may receive from touching certain objects.