Hoodoo and Voodoo have many things in common, but there are also differences.
Voodoo is a religion and Hoodoo is an African American system of folk magickal practice. When evangelizing Christianity became a large movement in the states, many of the African slaves were “required” to convert from Voodoo to Catholicism. As you could imagine, being told to change your religion would be very difficult. What came from this transition from Voodoo to Christianity for the slaves is what is now seen as Hoodoo. Many Hoodoo practitioners are also Roman Catholic and see themselves as spiritualists. Hoodoo practitioners call on Catholic Saints in place of loas, the African gods of Voodoo. With Hoodoo, one will see spell work that involves Psalms from the bible, candle lighting as well as other Christian influences.
In the Voodoo religion, similar to Catholic, each Loa/Lwa (like the saints) is know to help those that call on them for specific problems. Also like in Catholicism the Loa (saints) petition God on the believers behalf. From what I understand, the offering of sacrifices dates back to B.C. times. Blood is seen as the life force and in some rituals is offered as a sacrifice. The reasoning and justification of these acts (to Christians) is that before Jesus died on the cross for our sins it was quite common to sacrifice animals. But, animal sacrifice is certainly not something that is necessary for all voodoo rituals.
I’m sure there is more to it than that! I was very discouraged when I initially asked this question myself and hope I can provide you with clearer answers moving forward. Maybe we will have a guest blogger! ^.^