This is one type of a Safety Switch. Safety switches save lives by monitoring the power leaving the switchboard and what returns to the switchboard. If a Safety Switch detects a problem (a leak) it turns the power off really quickly to save lives and property. Safety Switches always have a test button and should be tested monthly.
This is an Earth Stake it connects your house to the earth, it is driven into the ground, there should be one on the outside of your home where it is exposed to the weather. Earth Stakes are a vital part of your homes safety.
