What are GFCI Receptacles

 Simply put, they protect you from shock hazards.

A Hazard can be considered as a situation.
Think about it like this.. The GFCI is a computer that senses something is not right with the appliance that you may be using and decides that for your safety, I m not going to let you use this
because you may get hurt.

This is not to say that the appliance is bad, or won t work in an unprotected socket, but it s not safe, so I won t let you use it.