Okay, maybe I'm over simplifying here, but as someone who's had a life-long ability to read objects and locations, I'm going to call it what I want. What many refer to as "residual" hauntings, I like to refer to as a "Green Haunting" (I'm all about reframing things so they're not so dark and threatening--the paranormal has too long been dictated by evil-vs-good, church-vs-devil).
In a green haunting, a location could be stuck in an ideal situation (whether it's geological, running water, construction of the building, or history of the land), in which it can recycle events over and over again, picked up by the six senses.
Sometimes it's just sounds like footsteps, doors closing, a cough. Other times, it can be a scent of roses, cigars, or sulfur. Other senses can also be involved like the sense of touch giving you a feeling of someone brushing against you, pulling your hair, or the hairs standing on end on your arms. If it's visual, it could be a shadow traveling in the same direction down the hallway, a light that flashes, a full-body apparition. We are creatures who gain our information from our senses and folks who've gone ghost hunting can tell you, that even the sixth sense can be a potent warning sign.
The sixth sense will activate in ways you often hear from people who have experienced hauntings or gone to haunted sites. The feeling of being watched, a sense of doom, hairs standing on end, an icy cold, a tingling feeling as if something traveled through your body and gave you deep shaking chills.
If you think of these repetitive "haunting" characteristics as something recycling through space and time over and over again like a loop, sometimes your sense of smell catching them, sometimes your sense of touch, you can appreciate the intriguing mechanism of hauntings.
I'm not convinced in the idea of intelligent hauntings, but I'm open to finding out if there's a way to prove it. A person can ask a question to someone in a room and have the TV commercial in the background"just happen" to answer it. You can also ask questions of "ghosts" and get answers that sound fitting, but that isn't real proof of interaction. It's a huge jump to go from what is obvious to anyone who's lived in a haunted site, the repetitive and random things that occur, and something intelligent trying to get our attention.
Ghost hunters are faced with the same issues homeowners are. We go to a site for perhaps 5-10 hours and if we're lucky we capture about 0.25% of what occurs in a given year. It's a crap shoot, but when we do get something, it's hard to correlate that what occurred was a reaction to what we asked or did. I can't tell you how many times I've asked a question to get a knock or sound of an object moving which I assume (because I'm trying to make communication) was done for my benefit. Should a once-live being really exist in another plane and be able to respond to our questioning, we'd have been screwed long ago because how many of us have talked to deceased relatives without one single sound, one single response? If anyone wanted to talk to you specifically from the other side more, who better than a relative who cares for you and misses you?
There's nothing to say that replayed events in a location aren't activated by, as of yet, some unknown mechanism. It could be reflective of the emotions of the people living in the home. I know that many times when my family had emotional issues when I was growing up, the house was more active. Could strong emotions imprint an event and then release it later on? If you yell at a ghost and taunt it, will you get more response? I believe that's very possible and we can witness that on many ghost hunting shows that are popular nowadays. The logic-minded person might say that a KII meter going off could be caused by the person using it having energy at high levels, being kinetic, causing it to go off, or that a person raging at a ghost might release a sound or event by an emotion that originally locked that event into that space. It's a line of experimentation I'd like to continue to follow.
For now, all hauntings to me are green hauntings. I'd like to find something other than recycled echoes of the past, but it might be reassuring to homeowners with issues to know that these things are random and not directed at you. Someone in the past might have screamed and cried in that room when they got bad news, someone might have banged on the walls in rage. It's not you. It's the place and space and time and the right conditions meeting to "recycle" a phenomenon.