There are people who dabble in the black arts, channeling, soothsaying, etc. They are considered witches. The Bible speaks of witches and those possessed with familiar spirits (demons). Yes, it's real and any and all contact should be avoided with such individuals. The demons can be cast out, but only by someone with the Spirit of God living in them. If the person doesn't want to be delivered, sometimes you can't cast the demon out.
Make sure if you are someplace where they are trying to cast out a demon, that you are not near the person when the demon comes out, if your living is not right. It's looking for a new home. You must be protected with the Holy Ghost living inside you. That seals you from evil. Otherwise, you could be it's next home, if you have an "open door" in your life, for it to enter in. The Lord and satan cannot inhabit the same body.