Wikipedia
The Vodou temple is called a Hounfour, and the leader of the ceremony is a male priest called a Houngan, or a female priest called a Mambo.
At the centre of the temple, there is a post used to contact spirits, and a highly decorated altar. There is a feast before the ceremony, and a particular pattern (a Veve) relating to the Lwa being worshiped is outlined on the temple floor.
Dancing and chanting accompanied by beats from rattles and religious drums called Tamboulas begins. One of the dancers is said to be possessed by the Lwa, enters a trance and behaves just as the Lwa would. An animal, normally a chicken, goat, sheep or pig, is sacrificed and their blood is collected. This is used to sate the hunger of the Lwa.
Their religion was founded on the idea of one supreme God – an unknowable but almighty force. Under Him there lies a network of Lwa or spirits, which are broadly equivalent to the Christian idea of patron saints. Each Lwa represents a different area of life and has certain qualities. For example, if a farmer was worried about his crops he would focus his worship on the Lwa known as Zaka, the spirit of agriculture.