"Black" When used with Magick denotes a person of evil trying to work in Magick.
"Magic" is the illusions and tricks done for entertainment for audiences.
"Satanism" is rituals as put forth by one of the minor Christian Gods and has nothing to do with Magick..
That said, the kind of person likely to be drawn to malicious magic and the type of person likely to be drawn to sensationalist "Satanism" are very likely similar. The two things are definitely not the same, but a person involved in one may very well be involved in the other.
More likely than not, the person is just full of BS.
"Black magic" is a loose term... it can denote the use of magic for purposes of harming others, or it can denote the practice of summoning and constraining demons to accomplish a task. The latter often utilizes long drawn-out rituals, fasting, chastity, and lots of prayer to the Judeo-Christian God prior to the evocation. As such, it is not worship of the devil, but still utilizing otherwise evil forces for various purposes.