This comes up in one form or another over and over and …
Ground / earth / 0V
These are confusing as ‘ground’ and ‘earth’ are used both interchangeably and as to mean 2 different things, made worse by differences in English between different English speaking countries.
There is a connection to the muddy stuff outside.
There is a plane on a PCB, or in past times the chassis of the electronic system, the plane or chassis being the common connection for everything.
There is a point in the circuit designated by the designer as 0V, from which everything else is measured.
In the UK (I don’t know about other countries) the earth connection in mains wiring used to be connected literally to earth with a stake in the ground outside the property, or often to the (then) lead incoming water pipe. More recently PME (protective multiple earth) was introduced. Now the earth connection is to the incoming neutral, with the connection made before any meter, switchgear or other equipment.
More than one 0V
There is the repeated misunderstanding by people new to electronics where they have 2 separate power supplies but don’t see the need to connect the 0V of one to the 0V of the other. For some reason they are blind to the need for there to be a circuit back to each respective power supply and this includes for signals from the part of the circuit fed from one PSU to parts of the circuit fed by the other. Maybe this needs a tutorial all of its own, I don’t know.
The need for pull up (or down) resistors
In my mind this is also part of the same discussion, and something I have been thinking of writing about for ages.
How to proceed
If this is going to be a tutorial and a joint effort, then I suggest refining the above list to one we all agree on, then writing the text and producing diagrams and schematics, then, when we are happy everything is good putting it into one complete tutorial which can be pinned somewhere.