What is the difference between spirit, soul and ghost?
A spirit or soul is the same thing. If you translate from the Hindi word Aatma, the proper translation is "self," instead of soul/spirit.
The only difference between spirit/soul and a ghost is that spirit/soul exists in all living beings. A ghost doesn't have a physical body.
When someone leaves their physical costume due to any reason, the body is a corpse. And the detached soul is a ghost.
Every living being, humans included, have a subtle body within the physical body. It's also called astral body, energetic body, etc. It's this subtle body that goes out along with the soul, after death.
Depending on the deeds and traits of the human soul who died, you can call the ghost a good one or a bad one.
Once outside the physical body, a ghost has much more power as it's not limited by a physical body.
The bad ones scare and disturb others. They enter others' bodies to fulfill their unfulfilled desires. And harm them in any other ways.
A tantrik or a spiritual person can see the ghost. They would recognize whose ghost it is, if they had seen the person before death. This is because the ghost's subtle body has similar shape and face to the physical body it left.
God is a spirit and we were created in His image. So we are also first a spirit we have a soul and we live in a body. Our spirit is who we really are, our soul is our thinking, reasoning, our mind. Our body is the house we live in while we are on the Earth. There are no ghosts only demonic spirits. And demonic spirits are influences that infect or possess people. They can only be influenced or possessed by giving that demonic spirit a doorway to enter them and that could be many different things. Pornography, demonic movies, are places that have allowed Satanic rituals, are any type of luciferian worship. The Battleground that the devil uses is your mind and so you must fill your mind with things of God the word of God worshiping and praising speaking the word of God will cause demons to flee and you may have to do this repeated times because the devil does not give up easy but God is more powerful his word is who he is, Satan cannot stand to listen to it and so he will leave. If you feel that you are seeing a ghost, that could be a satanic spirit tormenting you. You must deal with that quickly with prayer, with the word of God, rebuke Satan and send him to the pit of Hell, in the NAME of Jesus, he must obey you because you have authority over Satan if you are a Christian.
A ghost is the spirit of a deceased human (or animal from the material plane, theoretically).
The difference between soul and spirit is typically seen as the soul being the immortal "portion" of a lifeform, and the spirit being that which contains the personality and fades away after the soul ascends. I have issues with this particular setup.
I work extensively with spirits, and if I were to say "I work with souls," that would be misunderstood as some sanctifying process. I work with beings who don't have tangible bodies on our plane of existence. This does not mean that they have no tangible bodies anywhere.
I see reality as a multiverse, with infinite parallel worlds, and with more evolved ("higher") and less evolved ("lower") planes of existence. Some of the spirits I work with have tangible bodies in parallel worlds. Some seem to have tangible bodies on more evolved or less evolved planes of existence.
When we think of ghosts, we imagine them as bodiless (yet somehow retaining a "physical" appearance); however, when we think of the afterlife and meeting up with our dead loved ones again, we think of them as once again tangible to us, because we will share the same plane of existence again. Right?
So the whole spirit/soul/ghost confusion is compounded by our minds' insistence that none of these things have bodies or can be tangible. This is important, because we know that there are reports (and certainly stories) which specify harm being done by suddenly tangible ghosts, or help being rendered by suddenly tangible, usually spiritual, angels.
Everything intangible can be chalked up to "spirit," and then differentiated based on its nature - ghost, demon, angel, deity, all that. "Soul" becomes a useless term unless we want to address the purity/goodness/evilness of our natures. It's not a functional being independent of the animate expression of us (the spirit).
Anything spirit is tangible somewhere, sometime. Souls, not so much.
What is the difference between spirit, soul and ghost?
It depends greatly on your chosen mythology, dictionary, and gaming system and RPG world. [I'm an atheist. We don't believe in any of this stuff, but it can be fun to conjecture.]
Some religions believe in all three as separate, some indicate at least a relation between them but they all represent states of the life and mental energies of an intelligent sentient being.
Dictionaries offer some insight into each word, all of which have various meanings. Spirit can refer to alcohol. Soul can refer to the essence of even an inanimate object. Ghost can refer to a disembodied spirit or a memory.
Gaming systems, well don't get me started. Some RPGs revolve around the supernatural (Call of Cthulhu anyone?), while others (most sci-fi systems like Star Trek, Star Worlds, Gamma Worlds, Traveler, etc.) have no rules for such concepts. The RPG world offered by the GM (Game Master) can vary wildly, more so than the ruleset used. Just speak with the GM for answers in the supernatural arena. Good luck. :)
In the spirit of the OP's most likely direction for the question, I'll say this. All three (spirit, soul, ghost) are words used to describe a fabricated concept of what makes us human, our "divine energy" so to speak. Each carries an intonation of some aspect or condition of the energy. Soul typically means the energy in a living person. Spirit usually means the soul, having left the body, now travels towards its afterlife. Ghost most often indicates a soul lost on the ‘road to home' and stuck in the mortal plane.
Soul: "the immaterial essence, animating principle, or actuating cause of an individual life" - Merriam-Webster
Spirit: "an animating or vital principle held to give life to physical organisms" - Merriam-Webster
Ghost: "1. the seat of life or intelligence," "2. a disembodied soul" - Merriam-Webster
Notice that Ghost references Soul, and it comes from a Germain word for Spirit. Spirit comes from Breath, and the definitions of Soul and Spirit are basically the same.
In general, Spirit and Soul are interchangeable, and Ghost is a manifestation of a spirit/soul. People draw distinctions between entities that have passed on verses ones that have stayed here, but I have heard all possible arrangements used by different disciplines, so pick the one you like and run with it. Just be aware that anyone you talk to could easily be using a different definition.
"Ghost" refers to the energy of a human body that has been left behind after death. The laws of physics tell us that energy can neither be created nor destroyed, so there you go. A ghost is an entity that lingers in a place after physical death, and is tied to the place for some reason, unfinished business, confusion, fear of going on to the next stage of life, whatever.
"Spirit" refers to the human energy that has crossed to the Other Side, and has chosen to come back, either to visit still-living loved ones, or because they have an affinity for the place they haunt.
"Soul" is used to describe the energy that drives all humans during their time on Earth. A soul is the energy of a living person.
This is the way I (and some others) think of the distinction between these three concepts. Take from it what makes sense to you.
A spirit is a kind of adult beverage.
Soul is a genre of music.
A ghost is a guy in a sheet on Scooby Doo.