Events that are recalled in regression hypnosis sessions may have no basis in truth or fact. But they are very real experiences. In any given event, the Conscious Mind is being bombarded by much more information than it's capable of processing.
This means that Conscious recall of any event is only going to be partial. The Subconscious Mind, on the other hand, is the emotional part of the Mind. It's responsible for holding onto all our emotions and memories and it's primary concern is safety. That's Law #1. If a situation in the past was perceived as a threat, that information will get stored in memory.
This is good! This ensures we'll know how to respond to similar situations in future. The problem is that the Conscious Mind can't process all the information, so it doesn't have the whole story. The rest of the story is being stored at a Subconscious level of Mind.
Often, these events are recordings of the perceptions, thoughts and feelings of a child! If an event in the past caused the client to experience uncomfortable feelings, and those feelings didn't get resolved, they can generate unwanted symptoms later in life - physically, mentally, and emotionally.
These are the kinds of issues clients are going to come to you for help with. And many of these issues will have their roots in childhood. This is what makes regression hypnotherapy so powerful! Hypnosis gives you access to the Subconscious level of Mind. Regression allows you to access memories that are stored at that level of Mind. This allows you to find out what happened to cause the client's problem. So, you can change the underlying story.