When you plug in a device into a receptacle that is grounded, you probably don’t think much about it, but that ground wire protects you from danger if there is a malfunction with an appliance or device that you are using. A short could cause metal parts to conduct electricity right through you, possibly leading to death.
While most homes will have grounded receptacles, there are some older homes that still have older, ungrounded receptacles. These will not protect you. Unfortunately, some homeowners will use adapters to enable them to plug in grounded devices into ungrounded receptacles. Even worse, some have installed a grounded receptacle into a spot where there is no ground wire, which makes it deceptive, especially if you weren’t the one that did the installation. Those receptacles might give you a false sense of security. While there isn’t an easy way to test if your receptacles has a proper ground, an electrician should be able to find out for you.