My understanding of the term 'dissociation':
Dissociation, when used in a psychiatric/medical context, usually refers to the fracturing of a person's identity or personality. There can be multiple causes of dissociation, one of which is trauma. Something traumatic happens to a person which completely overwhelms their ability to cope with the incident. This triggers a survival response during which one or more portions of the persons core, or 'heart', becomes separated into pieces referred to as 'alters'. There can be many kinds of alters with completely different functions.
An alter normally lives in the spiritual realm while the core will live primarily in the material world. The alter can express itself in the material world either by permission of the core or by overpowering the core and manifesting on its own. Some alters hold the memory of the trauma that induced the split and their purpose is to shelter the core from the devastation it would otherwise experience. Usually, when asked about the trauma, the core will experience amnesia and be completely unable to recall the traumatic event. In doing so, the core is able to 'survive' and continue on.
To understand DID I must have a practical, working knowledge of the spiritual realm. I'm afraid I understand so little about the spiritual realm. Jesus referred to this when he said,
“If I have told you about earthly things and you do not believe, how will you believe if I tell you about heavenly things?” John 3:12
The core is aware of the alter and will often speak of 'hearing voices'. Because most psychiatrists deny the existence of anything 'spiritual', their response is usually to tell the person the voices they are hearing are 'all in their head'. The tools of their trade are designed to investigate the material world, not the spiritual.
We who are followers of Jesus Christ understand that there is a very real spiritual world. The core is hearing voices from the spiritual realm, not from their 'head'. Unfortunately, we usually think of the spiritual world it as being a way off up 'yonder somewhere. Jesus tells us clearly that the spiritual world in all around us when he says in Luke 17:20-21:
“When asked by the Pharisees when the kingdom of God would come, Jesus replied, “The kingdom of God will not come with observable signs. Nor will people say, ‘Look, here it is,’ or ‘There it is.’ For you see, the kingdom of God is in your midst.”
I do know that the spiritual realm is home to both good and evil spirits. While neither the core nor the alters are demonic in nature, they can, just as we can, allow evil to enter them and influence certain behaviors. I refer to Matthew 12:43-45.
Very long post so I'll stop here.