What is the purpose of an Earth leakage circuit breaker ?

What is the purpose of an Earth leakage circuit breaker ?

Safety. There are two ways to get an electrical shock. One route is from live to neutral. That is not detected by a leakage breaker. The most common route is from live to earth. This produces a difference between the live and neutral currents. The ELCB detects this and switches off the electricity before too much harm is done.