A ground is a connection between an electrical circuit and the Earth.

Electricity naturally flows to the planet ("flows to ground") through anything that can conduct electrical current, and it is continually seeking such a path. The conductivity of concrete is enough to provide a path for deadly current when there is sufficient voltage available.

Living creatures conduct electricity: there are charged potassium currents in your body (in the 10-millivolt range). Nerve cells communicate to each other by acting as "transducers," creating electrical signals (very small voltages and currents) in response to the input of certain chemical compounds called neurotransmitters.

Resistance is the restriction that slows down or stops the flow of current. The more resistance a body offers to current, the slower electrons will flow for any given amount of voltage.

Voltage is the force that causes electrical current to flow. Voltage is not what harms you — it indicates the capacity for harm by electrical current.

Electric current doesn't just occur on its own: there must be voltage available to motivate electrons to flow. Some people have survived shocks of several thousand volts, while others have been killed by as few as 12 volts. It is electric current that burns tissue, freezes muscles, and fibrillates hearts.

Voltage is always relative between two points. No voltage exists between electrically-common points.

Current (amperage) is the amount of electricity that is flowing.

Whatever electrical items you have plugged into the circuits of your home can transmit a fatal amount of current—but only when certain conditions are met.

You are unlikely to feel a shock at 1 milliampere or less. You can sense a shock but easily release your grip at 1 to 8 milliamperes.

Ten milliamperes (10 mA or 0.01 ampere) of electricity can deliver shocks ranging from severe discomfort to extraordinarily painful.

Currents between 100 and 200 milliamperes (0.1 ampere and 0.2 ampere) are fatal.