I have seen some explanations for each of these as to how each of them separately are different from the other. To understand them all better, I wanted a cohesive, specific answer on how and why they differ in safety for humans, as well as protection for equipment from power tools to computers, how surge protectors will work with them etc.
A properly grounded 3-prong outlet protects against these types of faults:
- short to neutral or ground should trip the breaker.
- open neutral will not cause a hazard.
- a heavy load will raise neutral voltage (due to wire resistance) but ground will remain at 0V.
- in addition, electronics will be properly grounded and surge protectors will work properly.
A bootleg ground will protect against a short but
- open neutral may put full line voltage on the ground (through the device plugged in) producing a lethal threat.
- a heavy load will raise ground above 0V, causing a hazard.
A grounded GFCI will provide the characteristics of a grounded standard outlet plus
- current flow between hot and any ground (presumably through a person) will trip the GFCI and prevent electrocution.
An ungrounded GFCI simply removes the grounding for electronics: some sensative devices could malfunction and surge protectors will not work correctly.