Voodoo, means "spirit," and may be one of the world's oldest practices for honoring nature and traditions. People celebrating voodoo ceremonies believe that disembodied spirits, called "Loa," are sometimes loving and good, while others are demonic. Haitians believe that the Loa most often express their displeasure by making people sick. To prevent this, Haitian ceremonies "feed" the life energy of a sacrificed animal back to the Loa. Some spirits then communicate prophecies, advice, or warnings to a believer. The Practitioner may be a long deceased houngan or mambo—priest or priestess of a past voodoo ceremony.