When traumas occur, they often get recorded on an "island" of the brain, cut off from communication with the rest of our brains. Since these islands don't get the benefit of new information, those memories exist in us, frozen in time. They are frozen in PARTS. There are many therapy models that work with 'parts', Internal Family Systems, Structural Dissociation, and Schema Therapy to name three. I
believe EMDR is also a 'parts' therapy--because our traumatic memories are stored in parts--but this is not explicit in the model. Helping a client to understand and work with their parts, can be non-pathologizing, and can greatly improve their progress!