I am connecting a wirering that was done for me, I came across an unfamiliar connection, that is 4 wire cable from light switch to light bulb, how do I connect this , I am only familiar with life, neutral and earth wires, which one is the 4th one, and why 4

The 4 wire cables actually are called 14/3 and 12/3 for 14and 12 AWG. The ground is assumed and the 4th wire.

4 conductors are needed for some 240 circuits that need a neutral. It's also used for 3 phase.

In the home, it's typically used when wiring 3-way and 4-way switches where a light can be turned on or off from n locations in the home.

Using x/3 cable from the switch to light when the light has the powered conductors to it.

This allows a number of options. Ceiling fan and light combos controlled from the wall. Regular switch loops (use red and black) and the use of timers and other home automation devices that require a neutral. The whites can be capped.