The electrical grounding & earthing can be divided into the following three areas with respect to purpose: Neutral Point Ground, Safety Ground, Equipment Ground.
Neutral point grounding
(e.g. resistance, solid, reactance).
The purpose is to establish the ground reference of the system. The neutral ground connection is usually made to the neutral of equipment like generators & transformers.
This is made for protecting personnel from injury and property from damage. These connection are made to parts of the system that are usually not energized but may become under abnormal or fault situations.
Grounding made to ensure a low impedance return path for ground current should an electrical fault occur.
Between live conductors and equipment enclosure, in order to secure that a trip of the faulty circuit is made in a short time.
These three grounding systems are required to be kept separate except for a connection between the the systems. This prevents differences in voltage potential from a possible flash over from lightning