Hah. Define "exist".

Shamans, marabouts, "de-witchers", etc, do exist, in the sense that there are people who have this function in many societies. What they actually do may be more psychological and social than downright magical, granted, but still, our world is full of them. They do impact societies and lives (of believers), both positively and negatively. But they fulfill the function that is expected from them (basically: attributing fictional meaning to life's chaos and helping people deal with it), and that's why they endure everywhere.

And, beyond that, there may be actually non-existing ones, in the sense that so one plays that role (self-identifies with it), while people still accuse each others of being one, and act in accordance to that belief (with fear, paranoia, revenge, trials, accusations, retaliation). But there again this belief may make it exist : when people's consensus designate you as a witch or sorcerer, your only social and psychological defense may be to embrace this role, and use it to gain status (to use the fear of you as a weapon) instead of getting destroyed despite your denials. So, you "become" one. Making it exist, and not exist, but hey, exist. Just like policemen exist because they wear the uniform and people around them behave accordingly to its meaning.

So, for the OP : There's usually a distinction between "witchcraft" and "sorcery" in english (not really in french), according to which "sorcery" is mostly innate (evil eye, etc) while "witchcraft" is a deliberate craft. But these descriptive categories are tough to use. They are often (loaded) foreign words trying to translate local concepts, in order to sort them out, and to make (sometimes valid, sometimes undue) comparisons between cultures. They can be handy to use, but it's always worth deciding and clarifying yourself what the words mean to you before using them, if you really wish to communicate an info. "Shamanism", for instance, is a strictly siberian thing. But it's been used to designate many similar practices throughout the world, according to some shared elements (in this case, the ability to communicate with spirits, or to travel in the spirit world, through ceremonies and rituals, in order to influence the physical world : health, weather, etc). So you can always nitpick on whether this or that should or shouldn't be called "shamanism" aswell. I'd say the closest thing to shamanism that I've seen in a videogame is the "legacy of kain" vampire. But AD&Ders are free to do with "shamanism" what Romero did with "zombies". It's just a matter of re-defining the word locally.

So, in videogames, usually, sorcerers are mystics and magicians are scholars. It's pretty arbitrary. Zero reason to take these distinctions seriously in fiction, it can be misleading. Even in science, the meanings fluctuate a bit, and those people are actually trying to define a universal consensus on the concepts. Humanity is complicated. And videogames don't even try...

There. *pushes glasses back up on nose without touching them*