Dissociation is when someone disconnects from their thoughts, feelings, body, environment, memories, and/or sense of self. It is a very natural process that everyone experiences to some degree. For some, dissociation becomes a frequent occurrence that can be problematic for them, which may then be classified as a "dissociative disorder." The root cause of a dissociative disorder is often linked to repeated experiences of trauma in childhood.
Dissociation can be thought of as being on a spectrum - on one side of the spectrum someone experiences a very typical style of dissociation - while watching TV you tune out those around you, or while driving, you find yourself at your destination without remembering the drive. On the other side of the spectrum, a person may "come to" after several hours of time, with no recollection of what they've done. This could be a persistent problem, and the person may even find evidence that they had been doing something during the time they can't remember, even something completely out of character for them.
In the middle, there are all sorts of dissociative experiences someone can have. Often I work with people who either feel numb most of the time, or when they have feelings, there is a sense that it is "not me." This can be true of the body as well - ie, "I know I hit my hand on the door because I saw it happen, but I didn't feel it."
Someone may also feel that they swing rapidly from one perspective to another. This can be disorienting and cause someone to act out in a way that they later regret. A person may be aware of how they acted, but they may not feel that it was them who decided to act that way. With this, there can be an intense experience of internal conflict.
Another example of dissociation is that someone may find that they get absorbed in reading, daydreaming, or watching TV for hours. They may almost "come to" to realize their mind has been in a fantasy zone for quite some time, and things that they were hoping to accomplish have been left undone.
There are so many ways that dissociation can present itself. Many people do not recognize their struggles as a form of dissociation, and that may be because of the vast differences between how each person experiences dissociation. As far as a "typical" presentation of a person who dissociates - there isn't one.