SHAMAN-(Siberian Tungus language) a spiritual leader, a medicine man/woman or witch doctor. While a medicine man will tend to the sick, working with herbs, barks and the like, the shaman works more on the psychological level. He will go down on "a journey" for the benefit of the one who is ill; he will direct sacrifices, he will seek out new knowledge, and he will accompany the spirits of the dead on their journey to the afterlife. ...

IN my case, i am the one who is ill and i do my trance and journeys
to benefit myself pschologically.

A shaman has a different role depending on the society.
i tend to lean toward the toltec shamanism (Carlos Castenada-The Teachings of Don Juan) to experience dimensions unknown to the scientific world and
gain futher insight into the spirit world and learn new truths.

yes there are shamans who use/experience hallucinagenics as their ally
in their practices.