This is an expansion on the topic of grounding for technical purposes, there is a similar post, but this goes into more detail.
When I was in college, it was a little confusing when professors kept referring to ground as “just a reference point” and being a literal connection to the Earth. I now know there are different kinds of ground and have their own purposes. This will be split into two parts for the sake of brevity. Let’s talk about Earth Ground.
Earth Ground
Earth ground is almost self-explanatory, it is a connection quite literally to the Earth. The Earth has an enormous resistance, has high conductance in moist areas, and low conductance in dry areas. Electric code states that the rods needed for buildings need to be driven underground to have contact with at least 8 feet of dirt. Some rods may actually need to be stacked together to be driven deeper in dry areas. The practice of grounding (especially with AC systems) is for our own safety and safety of appliances electronics. Since the Earth is a great conductor in moist areas, it provides a path for electricity if there is a fault so that it won’t flow through you as easily. Electricity always prefers the path of least resistance. Here are a few symbols you may see in diagrams:
This symbol is always supposed to mean that there is a connection directly to Earth ground. Appliances such as fridges and stoves are “Earthed” or have their input ground wire (green) tied to their chassis. If there was a fault in the appliance and electricity was passing through the chassis, earthing has the potential to save your life as the path to Neutral wire and/or Neutral at your electricity cabinet is very likely to be much lower than the path through you. Under normal circumstances, electricity hardly passes through the Earth rod and back to the source as Earth has a huge resistance compared to the Neutral wires in your house electricity. This is why GFCI outlets and GFCI breakers exist as an extra back-up for safety. Electronic products are supposed to have a third wire on their AC inputs for this reason and two prong applications are much more dangerous in comparison.
Here is the link to the next part: Getting Grounded Part 2: Signal and Chassis Ground