Some are, some are not. 'Residual' ghosts are just a force without any sentience, like a replay of a past event. They cannot interact. 'Real' ghosts are sentient, can interact and communicate. 'Shades' (aka shadow people) are earthbound spirits that have been on the earth plane so long they have evolved/devolved into something more than just ghosts. They are sentient, can interact, communicate, move objects, induce glamour, temporarily possess, read minds, etc.