Electricity needs a reference to ground, meaning the ground connected to Earth. When voltage comes in contact with ground, it will trip the circuit breaker or have a point of ground to prevent energizing things that are not meant to be energized. Grounding is for your safety.
How do you tell if your house is properly grounded? You will need to have ground rods, cold water bond with a properly installed main bonding jumper, and grounding run to all energized locations. To the untrained eye, it is hard to tell if proper grounding is present. Your safest option is to have a qualified electrician verify that proper grounding is in place.
