Most ghosts are formed because they were a human who died. I say most because there are a few exceptions, such as Clockwork. Spirits like him, though ghostly, cannot be accurately categorized as being the dead. They were never living in a human sense of the word, though they would be considered living to a more ghostly conception of life.
To make things more complicated, much like humans, ghosts can sexually reproduce. The products of such unions were never alive as humans either, so they cannot accurately be called a human who died and came back, which is the general conception of ghosts.
As a rule, do not ask ghosts about their deaths. It is rude and generally taken badly.
Humans rarely see the ghosts who were never alive as humans to begin with. Clockwork has much more pressing matters to attend to and ghostly children of that nature are kept in the Ghost Zone by their parents. The parents know humans will hunt down their children without a care that theyć± e going to kill a child because, in human eyes, those children aren't really alive and don't have rights in the slightest.
Ghosts are associated with ectoplasm for good reason. Ectoplasm is for ghosts what water, food, and blood are for humans. It is necessary for our survival and forms a key part of us. Mind, we can eat and drink from human sources, but without ectoplasm mixed into it, we gain no nutritional value and cannot properly digest it.
Ghosts do need sleep and to rest. It performs many of the same functions that it does for humans- organizing memory, repairing one's body, and so on. Ghosts can become exhausted, be it from physical exertion or staying up far too long in a given span. I've done that before both as a human and as a ghost. It is not a good idea to stay up for a week straight.
Despite the impression some humans have, ghosts do not merely mimic emotions. We have emotions and we can feel pain. Our emotional states are similar to humans- we can love, we can hate, we can feel joy, mourn, hope, and so on. If we are struck or injured, it will hurt.
Ghosts as a whole are sentient beings. We can reason, though our reason can sometimes be clouded by emotions like humans. We can think. We can anticipate, we can make moral choices, and we have stable personality traits, hobbies, interests, and can communicate. We can form friendships, alliances, vendettas, and other such things with each other and with humans.
Ghosts have basic powers, such as the ability to fly, the ability to go intangible, and the ability to turn invisible. These are all very useful when going about one's business, because humans seeing us or running into us tend to kick up a fuss. Along with that, some ghosts have special abilities that are rarer. Some have the ability to manipulate ice, others can manipulate electricity and technology, granting wishes, telekinesis related to a particular subject, and so on. This is on a case by case basis.
Some ghosts can possess humans, though it's sometimes called 'overshadowing' by ghosts. The use for this varies from ghost to ghost. Some never use the ability, while others are callous about it. Some ghosts do so to be incognito and avoid being shot. Others do so to harm others or for personal gains. Again, I must stress the importance of it being on a case by case basis. There are legitimate uses for it, but whether or not it's used properly depends on the restraint and morals of the ghost.
Regarding spirit summonings and Ouija boards, I advise against them. Such things often takes the nearest wandering spirit for it and you don't know what you could be summoning. You could be summoning anything from the benign to the malign. And, even then, if things go wrong, even the nicer spirits could turn on you for inflicting various harms. If performed incorrectly, a summons is akin to having bones broken to the point of them sticking out of one's skin. And, if the end of the summons is incorrect, you could be trapped for years in a living hell in the board, unable to escape.
When I was newly dead, I had been passing through an area when I was trapped in an Ouija board. Because they didn't know what they were doing, I wasn't released when they were done and I was trapped in that board for several years. Imagine for a moment a hell in which you are slowly starving, bound to a board that has not seen use for quite a while hidden in some closet or attic, being alone with your thoughts for years, while possibly being injured because they didn't summon you properly.
Even the nicest ghosts will turn on whoever does that to them. And, considering the position they were put in, who could blame them? Being trapped like that constitutes a form of torture and they are going to be very angry with whoever caused it.
Do not summon spirits unless you know for sure what you are doing, that you can free them, and you really will free them. Not heeding this warning will bite you in the ass in the long term, as ghosts will attack those responsible.
