Tell me about shamanism

Facts, opinions, experiences, etc.

No one knows anything about it?

Spiritual tradition is many tribal cultures around the world. The most famous being in South America and Siberia. There are shamans in pretty much every cultures past. Yogis, Druids, Medicine Men, Voodoo, Priests, etc... To put it simply, they perform the function in society of leading the group through spiritual experience.
There is a lot more I could say but I will leave it there for now...