Activated Charcoal is a form of carbon processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions.
Activated charcoal draws bacteria, poisons, chemicals, dirt and other micro-particles to the surface of skin, helping you to achieve a flawless complexion and fight acne. Charcoal is not metabolized, adsorbed or absorbed by the body, but it can be used to treat some poisonous bites and disinfect some wounds. Activated charcoal powder is proven to adsorb thousands of times its own mass in harmful substances, which makes it a popular ingredient in facial masks.
Activated charcoal is used to treat poisonings and overdoses following oral ingestion. Tablets or capsules of activated carbon are used in many countries as an over-the-counter drug to treat diarrhea, indigestion, and flatulence.
However, it is ineffective for a number of poisonings including strong acids or alkali, cyanide, iron, lithium, arsenic, methanol, ethanol or ethylene glycol.
Incorrect application (e.g. into the lungs) results in pulmonary aspiration, which can sometimes be fatal if immediate medical treatment is not initiated.
Source: wikipedia, livestrong.com