The following is inspired by a true story...
There was once a man, we'll call him 'Mitch'. Mitch thought that he could easily change out the outlets and switches in his living room. Some of the outlets were partially controlled by 3-way switches. Not easily intimidated, Mitch looked up diagrams online and watched videos on YouTube to become knowledgeable on the adventure he was about embark on. Mitch thought he was prepared. He even took picutres. When he changed out the swtiches and the outlets, nothing worked right. In fact he tripped several breakers trying to fix the issue and sparks flew. Come to find out, the people that originally wired up his house, did not do it properly. And did you know that the configuration of switches has changed since the 1970's? Mitch didn't but if Mitch was a properly trained expert, he could have diagnosed that issue before beginning. Mitch's wife was irate with him because he undertook this project over Thanksgiving when they expected to be able to watch the big game on the TV in the living room. Mitch ruined Thanksgiving. Don't be Mitch.
Do you feel for Mitch? I sure do. But, do you have to go through what Mitch did? Absolutely not! Outlets and switches may seem simple in concept but are complex in reality. Electricity is dangerous and can easily be fatal. You do not want someone who is YouTube trained working on your home or business' switches or outlets. Incorrectly installed components can lead to fire, or electrocution. This can result in your appliances being destroyed and needlessly putting you and your family's lives in danger. You need a trained, certified electrician to ensure the job is done right for either residential or commercial applications.
A GFCI (ground-fault circuit interrupter) is a residual-current device that quickly breaks an electrical circuit to prevent serious harm from an ongoing electric shock. They are commonly found around places where one can easily 'ground' out, like by water, for example. They are required by code in areas like kitchens, bathrooms, hot tubs/jacuzzis, or pools because water is a fairly good conductor of electricity.