Read about why you should KYE (know your entheogen) here.
Salvia divinorum is a sage native native to the isolated Sierra Mazateca of Oaxaca, Mexico. It is also called the sage of the diviners, and is used by the Mazatec shamans in their healing and divination practices. They believe it is an incarnation of the Virgin Mary, and also call it ska maria pastora, or “herb of Mary, the Shepherdess,” among other names.
Salvia divinorum is from the mint family, of all things. The psychoactive compound in it is salvinorin A which is not an alkaloid like most entheogens, and is not chemically related to any other psychoactive drug. It is the most powerful naturally occuring psychedelic, active in only a few hundred micrograms (the range of LSD). Also, for some reason, it is LEGAL in most countries. Yeah, Google that.
The Mazatec use it for healing, as mentioned, in the way they use morning glory and mushrooms, although the trip is not as long or powerful as that of the mushroom (in their usage). Generally an infusion of 50-100 leaves is taken at night. Darkness and silence is required for the effects of the plant to take place. They say that ska maria whispers, so you need quiet to hear her. Any loud sound or light can bring you out of the trip. It is therefore taken in quiet locations so the spirit of the plant can do its work (and the compound will have proper effect).
It acts on kappa-opioid receptors and is of very low toxicity. It has no addictive properties, but is known to cure addiction. In fact it is commonly used by the natives to cure alcohol addiction.
Like all shamanic plants, the sage of the diviners is used to find out lost things, heal diseases physical and mental, and commune with spirits.
The below video gives a very quick overview of what salvia divinorum is. If you scrolled past all the above crap and just watch the video you should be good to go. But here is some further reading for your information which we certainly urge you to read.