Santer?a also known as "La Regla DE Lukumi," is an Afro-Caribbean religious tradition derived from traditional beliefs of the Yoruba people of Nigeria. The Santer?a/Yoruba tradition is comprised of a hierarchical structure according to priesthood level and authority. Orisha "Ole" or temples are usually governed by Orisha Priests known as Babalorishas "father of Irish" or Iyalorishas "mothers of orisha", and serve as the junior Ile or second in the hierarchical religious structure. The Babalorishas and Iyalorishas are referred to as "Santeros(as)" and if they function as diviners of the Orishas they can be considered Oriates. The highest level of achievement for males is to become a priest of Ifa (ee-fah). Ifa Priests receive Orunmila who is the Orisha of Prophecy, Wisdom and all Knowledge. Ifa Priests are known by their titles such as "Babalawo" or "Father Who Knows the Secrets". Ifa Ile or Temples of Ifa serve as the senior to all Orisha Ile in the Traditional Orisha-Ifa / Santeria Community. The Sacred Oracle of Ika-Fun or Ika Ofun serves as confirmation.
I don't practice Santeria, I ain't got no crystal ball. I had a million dollars but I spent it all. If I could find that Hina, and that Sancho that she found, I'd pop a cap in Sancho and I'd slap her down. What I really wanna know, my baby, what I really wanna say I can't define. I'll make it, yes I'm going on. Tell Sanchito that if he knows what is good for him he best go run and hide. Daddy's got a new 45. And I won't think twice to stick that barrel straight down Sancho's throat. Believe me when I say that I've got something for his punk ass.
If it is the same voodoo stuff we see in movies, I think the principle is spiritual (Dark side) or psychic or a combination of both. It's like deportingninsects into ones belly. Where I come from, some such sorcerers are reputedly able to kill by just spitting on the intended victim's footsteps. Spiritual healers, mostly of Christian orientation, are able to counter this. A prayer for protection, healing and deliverance may keep one safe.
Cathy provided an excellent answer. I would just like to add to it.
The principle is also of trading and empowering with the Orisha's (Greater Spirits/Gods). It is similar to saints in Christianity. You find a saint/Irish who has the experience/knowledge/power you need and ask him/her to help. You do something for it and it does something for you. Often a token gift will be enough, but not always. The priest or priestess often tells you what to give or do for the spirit and sometimes is willing to do it in your stead.
It's an incredibly spiritual religion. A lot of things people in this religion do is have masses, put flowers around their house (for example) in order to know about the spirits that follow them, and clean out the bad ones from their home. Many of the prayers are actually Christian prayers like "Our Father", and quite a few others. What many people don't understand is that you have to be baptized in order to participate in Santeria, and a lot of things have to do with churches, and Jesus. After all, Santeria has Catholicism in it's mix. Animal sacrifices are not done all the time, and if they have to be done it has to be quick and painless or else the Irish (saint) won't be pleased. It's not voodoo, or anything satanic. Don't pay attention to what the media says this is, because it's not like that at all.