It is good to know and understand the different types of earthing systems
https://en.wikipedia.org/wiki/Earthing_systemIEC terminology
International standard IEC 60364 distinguishes three families of earthing arrangements, using the two-letter codes TN, TT, and IT.
The first letter indicates the connection between earth and the power-supply equipment (generator or transformer):
"T" — Direct connection of a point with earth (Latin: terra)
"I" — No point is connected with earth (Latin: īnsulātum), except perhaps via a high impedance.
The second letter indicates the connection between earth or network and the electrical device being supplied:
"T" — Earth connection is by a local direct connection to earth (Latin: terra), usually via a ground rod.
"N" — the earth connection is supplied by the electricity supply network, either separately to the neutral conductor (TN-S), combined with the neutral conductor (TN-C), or both (TN-C-S). These are discussed below.