How do you explain Voodoo?

There are cultures that firmly believe in Voodoo.
I’m not looking for Wiki links. I’m looking for people that have had actual experience with Voodoo or Voodoo practitioners, and understand their beliefs. Or have personally researched Voodoo.
I am in contact with a man that believes he has coughed up live blacksnakes, and had something crawl out of his mouth and bite him on the chin. He appears otherwise lucid, intelligent and personable. Polite, soft-spoken, open.
I don’t know how to respond to his “curse”.