What is the function of the earth leakage relay in electrical circuits and can it protect people from electrical shock?

earth leakage used for the protection against electrical leakage in t hecircuit When somebody gets an electirc shock or the residual current of the circuit exceeds the fixevalue, the relay can cut off the power within the time of0.1s automatically protecting thepersonal safety and preventing the equipement from the fault resulted from the residual current.With this function, the relay can protect the circuit against overload and short circuit or can beused for the unfrequent switchover of the circuit under normal conditions.

there are many types of these relayes and circuit breakers

Have a look at this

wiki/Residual-current_device