Many people have made dissociation out to be something very complicated, explained only in scientific or psychological terms. In my opinion, dissociation does not have to be complicated. While science and psychology certainly have unique perspectives through which to view it, dissociation can be explained very simply.
Dissociation is anything that allows (or causes) a person to lose touch with some aspect of the reality of the moment they’re experiencing.
This can be something as benign and commonplace as “losing” one’s self in a book. Or the classically-cited “highway hypnosis” scenario whereupon a person driving from point A to point B arrives at their destination with no memory of the trip. On the other end of the spectrum, dissociation can be as severe as splitting off a part of the personality to cope with extreme and inescapable pain and terror. All of these examples are instances in which people lose touch with some component of reality in their present moment.
It’s important to realize that everyone experiences dissociation, to some degree. Our brains are made to allow for it in a wide variety of situations, and not all of those situations necessarily involve trauma. All experiences of dissociation occur on a continuum, from mild and normal, to severe and abnormal. The point at which dissociation becomes a problem is the point at which it begins to disrupt a person’s quality of life and ability to function.