There are four basic elements to electricity, voltage, current, resistance, and wattage.

Current is the flow of electrons and in measured in amperage. Resistance if the opposition to the flow of electrons and is measured in ohms. Voltage is the amount of pressure it takes to push the electrons through the resistance and is measured as volts. Wattage is the amount of work done or the amount of energy used.

When it comes to electrical shock it is the amount of current that flows through the body that is being felt or doing damage. The relationship of the voltage and resistance of the body will mandate the amount of current that will flow. Below are the amounts of current and the reaction the human body will have to this current flow as outlined by OSHA (Occupational Safety and Health Administration) and be found at this site;
http://www.osha.gov/SLTC/etools/cons...0most%20likely

1 mA - Slight tingling sensation
5mA - Average individual can let go
6mA - 16mA - . Commonly referred to as the freezing current or "let-go" range
17mA - 99mA - Respiratory arrest and possible death
100mA - 2000mA - Ventricular fibrillation nerve damage death is very likely
2,000mA or more - Cardiac arrest, internal organ damage, and severe burns. Death is probable.

References
NIOSH [1998]. Worker Deaths by Electrocution; A Summary of NIOSH Surveillance and Investigative Findings. Ohio: US Heath and Human Services.
Greenwald EK [1991]. Electrical Hazards and Accidents - Their Cause and Prevention. New York: Van Nostrand Reinhold.

Notice that there is only 100 milliamps between feeling current and the likelihood of death.