An antistatic bag is a bag that is specially designed to help prevent static electricity inside the bag. These bags are often used to store and transfer electrostatic sensitive equipment. If you have ever purchased a computer hardware device such as a hard drive, sound card, or video card it is likely it came inside a dark gray antistatic bag. The picture is an example of how an antistatic bag may look.
Remember that only the inside of an antistatic bag is protected, placing a hardware device on top of the bag and not inside of the bag will not protect it. In fact, it is often more dangerous to place an electrostatic sensitive device on top of the bag.
If you are planning on replacing or doing any computer repair having one or more antistatic bag as part of your tools can help make sure any removed devices stay safe.