First, set aside wattage for a moment, it's a derived unit.
The key units are amps (current) and volts (voltage aka potential difference). In the commonly used water analogy voltage is water pressure, and current is amount of water that flows through per unit of time.
It's the current that kills you. But voltage and current are related, in many cases by Ohm's law: current is proportional to voltage, with coefficient called conductance (the inverse of which is resistance). That's why high voltage is more dangerous.
The key units are amps (current) and volts (voltage aka potential difference). In the commonly used water analogy voltage is water pressure, and current is amount of water that flows through per unit of time.
It's the current that kills you. But voltage and current are related, in many cases by Ohm's law: current is proportional to voltage, with coefficient called conductance (the inverse of which is resistance). That's why high voltage is more dangerous.