Recommended · for beginners
What is Ground? Earth Ground/Earthing
Why people recommend it
Explains what earth ground is and why it works as a reference potential; people recommend it to anyone confused by the many meanings of ground.
In their words
For this definition as well as #5 and #6, watch this video, this video and this video.
alejnavab on electronics.stackexchange.com, Sept 2021. CC BY-SA.