In response to a previous blog entry entitled 500GB MacBook Harddrive Upgrade for Under $100, a reader asked about Electrostatic-Discharge (ESD). In particular, he asked, "Would using simple gloves (like you use in labs and hospitals) be enough to prevent frying any electrical component of the computer's innards [when replacing a hard drive]?" Because ESD is a major concern for people handling electronics, whether it's building your own computer or replacing a hard drive, I think the topic warrants a bit of explanation given its importance. If you understand what ESD is, it's a no brainer on how to prevent it.
ESD is unwanted electric current flowing from one location to another. Examples are lightning, getting a shock by a door knob or another person, or zapping your electronics with your finger. Even a few millivolts can cause enough current to fry a transistor somewhere (and there are millions of them in a computer) if it's not designed to handle it. In the case of electronics, you want to prevent undesired flow of current by making yourself be at the exact same voltage potential as the electronics, which is 0 Volts. Wearing hospital gloves won't do that for you. What they will do for you is decrease the chance that current will flow from you to the electronics because it acts as an electrical insulator. But different gloves have different insulating properties, and you can build up different voltage potentials, which are factors in whether or not ESD will occur.
The point of touching the ground with your finger, which I recommended doing before touching raw electronics, is to ground your body (make your electrical potential 0 Volts). The earth is at 0 Volts for all practical purposes. "Ground" in electrical circuits always means 0 Volts. That way if you are at 0 Volts and the electronics are at 0 Volts, there is zero electrical potential between you and the object and it's impossible for any electric current to flow. In fact if you wore lab gloves and touched ground it could prevent a proper grounding because it would insulate you from the earth and not discharge that potential. Your best bet in preventing ESD it to touch the ground or something "electrically connected" to it with an ungloved finger. If you really want to be safe, buy a wrist strap and use it properly.
For someone else's explanation go here.