Earthbound = A person who has passed on, but whose "soul" is still connected to this plane/earth. Earthbounds are more commonly referred to as ghosts. Earthbounds that have learned to control the energy around them and that choose to manipulate it are more commonly referred to as poltergeists.
Spirit = A person who has passed on, and whose "soul" has crossed over to "the other side" (some call this place Heaven).
Imprint = Residual energy left over from an event that took place in that same area. Imprints are like energetic blueprints that can play over and over again like a video on replay.
Then there are other universal entities such as angels, astral beings, spirit guides, shadow people, etc.
Earthbounds are the only types of entities that will actually "latch on" to someone or something. This means that they will go wherever you go until they either choose to or learn how to detach themselves from the person or object that are attached to. Earthbounds don't always know that they have passed on so sometimes they will attach themselves to someone or something that is or that seems familiar to them.
Spirits will not attach themselves to anyone or anything as they have a life of their own on the other side. ^_^ They will, however, visit their friends and loved ones from time to time.
Imprints are not sentient energies, nor do they contain sentient energies therefor they can not attach themselves to anything out of intention. The residual energy is simply "stuck" in that area because of the strength of the magnetic field in the area as well as the massive influx of energy that took place while the event happened. (i.e. murder, suicide, mass death/killing like in a war or bombing, altercations, confrontations, etc.)
Your Spirit Guides and Angels are always with you no matter what. Sometimes people sense these energies around them and mistake them for earthbounds if they are not "in tune" with their guides & angels.
Lower Astral Beings can sometimes follow a person, but they don't usually hang around for long unless they get a rise out of someone. They can be real troublemakers and tricksters at times.
Shadow People are only watchers. They do not give off a negative or positive vibe as they are neutral beings in the universe. Some people may be afraid of their presence, but that is simply a symptom of their ego and it's common fear of the unknown and not because Shadow People are negative energies. Shadow people will also never harm anyone, but they will also never help/assist anyone as they are unable to do so. I think of them as surveillance cameras for the universe. I believe the "Mothman" is a Shadow Person.
Of course, there is a lot more to all of this but that is the basics.