Don't want to read so much? I have done a video for you to enjoy!
Ghost in reality, or at least the ghost that we talk about in Taoism (our lineage) is not about those movie kind of ghost. We are talking about the real world kind of ghosts, and there is nothing "scary" about it. Ghost, the word, Gwai 鬼 is just a word that can be defined as "When something is done processing in a universe, it goes to the next station and continue, then the departed subject is a ghost". Just like when you are eating, the stuff that is done processing in your mouth and went down your stomach, those are ghost for your mouth, they are "dead" from the mouth department already and is supposed to be going downward to be finished and transformed into their next form, to the intestines, etc.
The ghost word in our Taoist magic is not only limited to spirits, because there can be what we call Ghostnergy, the power or energy of ghosts, which everyone got some of that stuff in their spiritual body, the Faat-Sun 法身. These energies are not "bad" or "evil", it's just that they all have this property of absorbing "light and power" and attracts things over be sucked up, etc. Light doesn't mean physical light, it means any energy producing power of all sort, is light. Success and progress of a business is also considered light for the business. Ghostnergy can be there to suck up the light of a business and make the business go bad, or it can suck up the light from a criminal act, and make the criminal act not sucessful and saved someone from danger. Ghost, can be energies, and they are not good or bad, they are just different from other energy type, and they can be used for some magic to do a better job than using the other types of energies, which does the job slower, or not as effectively.
There are other beings, spirits, or whatever "aliens" in other worlds, dimensions and places, and they can be also the ghost of our world, meaning that they are supposed to go cycle to another universe or world beyond them, but they came back to this place, and they are our ghosts. As you can see, ghost is a word, which represents some conditions and a pattern, if things fits into it, you can use the word already. Most of the time, when people have "ghost problems", it's often really just their spiritual body having their own malfunction issue and got sick, then the ghostnergy got out of control and caused many weird things to happen in the world here, with their physical body. Ghostnergy or these negative energies can also contaminates, spreads, just like a virus, and it can be dangerous if you are around a group of friends who are all into these ghostnergy.
These ghostnergy is not something you cannot see, you can actually see the physical body doing things in a certain way, to spot the symptoms for these ghostnergy and know what problem is underneath someone without even "seeing ghost". Curious? Watch the video above!