This type of haunting is what most people think of when they hear the word ghost. Unfortunately, these types of hauntings are very rare. An intelligent or traditional ghost is kind of like Casper in the sense that they interact with people. The most common belief is that the ghost is connected to the site or people in some way.
This falls into the realm of a "demonic" or an "inhuman" type of haunting. It is perhaps of other-dimensional origin, and is often possessed (no pun intended) of a quite hostile nature. Anyone who has up close and personally encountered a demonic entity in action never wants the experience repeated; no one I've spoken to, anyway! It often evinces a form of intelligence (initially similar to a "human" type of haunting) in that it may insidiously seem to anticipate the approaches of the person(s) it menaces, including any paranormal investigators who are endeavoring to rid a home of its presence. Endemic to this most unwelcome infestation is a pronounced psychological instability, distress or unresolved conflict on the part of a resident or residents of the household subjected to the demonic assault. Additionally, experience has supported the observation that someone originally had to have invited in the demon, perhaps inadvertently, either through scaring implements such as a Ouija Board, conducting séances, undisciplined psychic experimentation, performing magic ceremonies or by habitually conversing with unseen presences (imaginary friends?). It should be mentioned here that while some of these devices may at first appear to be utterly harmless and regarded as tools to aid in tapping into one's sub consciousness, the results can be likened to leaving open one's back door in a country setting. Now, you may only have some little squirrels and chipmunks wander into your kitchen, but odds are that eventually you'll find yourself facing down a bear, maybe a small cub, IF YOU'RE LUCKY. And keep in mind, where there's one "bear," others are lurking somewhere close by!
Portals aren't really a new concept, as we've seen them in a lot of sci-fi flicks. But in the real world, portal hauntings are considered controversial as there is little known and the idea is mostly theory or speculation. Portals are thought to be doorways to another world or dimension in which entities travel through. It's speculated that portals are not limited to one location, region or limited to sacred ground. Typically places that experience a wide array of different types of anomalous activity such as glowing balls of light, odd creatures, strange shapes, or unexplained mists or fog, are suspected to have a portal in which these energies are traveling back and forth. Graveyards seem to be a hot spot for these.
A residual haunt is believed to be activity of reoccurring or traumatic actions from past events that leave an imprint on the environment.This type is probably the most common type of haunting. Because its characteristics are similar to the intelligent haunting, people often mistake it for an intelligent/traditional haunting. Like intelligent haunts, some examples of activity are phantom footsteps, sounds, images, and scents. One major difference between this haunting and the intelligent/traditional haunting, is that this type of haunting is not considered to be that of a ghost, and there is no interaction with the living.