An explanation of various terminologies.
The term hoodoo has become a blanket-term used for the practice. The origin of the use of hoodoo for the practice arose in the 1800s. The current evidence suggests the term is not African derived. Instead, it appears to come from the Irish who used the term to mean "unlucky, cursed". The term hoodoo has kept the negative definition until more modern times when it has come to be used as a synonym for magic. The word hoodoo can be used as either a noun, a verb, or an adjective.
Roots or Rootwork
Among blacks, the term roots or rootwork appears to be the most common term used to refer to the practice. The name stems from the traditional use of roots and herbs. Technically speaking, a practitioner who doesn't work with roots is not a rootworker, but often the term is used as a blanket-term for the entire practice as a whole.
The term conjure is the oldest term used to describe the practice and was also used to describe Native American and European practices, as well as the practices of African Americans. This is because the term conjure is an archaic term synonymous with magic. In fact, the term conjure was also used to describe stage magic. There are references to "conjure", a.k.a. hoodoo and not stage magic, being practiced in the U.S. as early as the 1700s. It is likely it occurred far before that time, especially when the Native American practices are considered.
Voodoo is the preferred term for non-practicing whites who tend to label anything that has a hint of an African origin as being "voodoo". In fact, certain whites will even label Native American and other cultural practices as "voodoo". This stems from underlying racism. No matter what word you use, either hoodoo, rootwork, or conjure, the practice is not voodoo and will never be voodoo.
I cover what is referred to as "Louisiana Voodoo" in my blog below.
Juju is a West African system of magic that is very similar to hoodoo. The term juju has become a synonym for the practice of hoodoo, though it tends to be used primarily in Louisiana and may be used to refer to Louisiana Voodoo instead.
Christio-Conjure, a.k.a. Christian Conjure or Christian Magic, is the official academic label for the practice. This is the label that educated academics have used for the practice. The term is not used by actual practitioners.
The term "voodoo-hoodoo" is primarily used by non-practicing whites who actually seem to know better but who simply cannot shake the voodoo label. I mean, they use the hoodoo part so why don't they just drop the voodoo part? There are also individuals today who want to claim that voodoo-hoodoo is a separate tradition. Voodoo-Hoodoo is not a separate tradition. The people who use the term "voodoo-hoodoo" are just like the people who use the term "voodoo". Both groups are either ignorant of the proper terminology or they are operating under the underlying racism to label everything associated with African practices as being "voodoo".
Other Terms To Be Knowledgeable Of:
Candle Worker - A person who mainly only sets lights or works with candles.
Reader - A person who specializes in divination.
Treater (Root Doctor) - A practitioner skilled in the use of roots and herbs for medicine and healing.
"Two-Headed" - A term meaning having one head on the mortal plane and one head in the afterlife. A similar phrasing that I know from personal experience is, "having one foot in this world and one foot in the next".
Goomer/Gummer - A term that I believe may derive from the term "goopher". See: Goofer Dust and Goomer/Gummer.
Black Gypsy - Term having both positive and negative connotations. On one hand it is a term where the practitioner is identified with gypsies in order to communicate the similarities of what they do. On the other hand it is also a term to denote a fraud or scam artist.
Spiritual Worker (Spiritualist) - A synonym used mainly for a professional, a practitioner who takes on paying clients, but which any practitioner may also use to describe them self.