When your nervous system is subjected to trauma, it freezes the memory in the right side of your brain.
The right brain houses our feelings, sensorial and body memory. It is pre-verbal, creative and imaginative. The left brain is sequential, logical, linear and analytical. It is what tells us time and place. It holds our past and our future.
When a client reports that one moment he/she is highly functional and then the next moment he/she is severely incapacitated with a panic attack or flashback -- chances are he is reliving trauma. A smell, sound or visual trigger locates the client in the right side of the brain, reliving the memory and makes it hard for him to access the resources of the left brain ie. logic, sense of time etc. 

Eye Movement Desensitization Reprocessing connects the right and left brain. 
Many of us already experience the benefits of "homemade EMDR" when we go for a walk and notice to our surprise that our "brain clears." The left and right activation of walking utilizes both sides of the brain ensuring that intense emotions and experiences are processed with the resources of both sides.
With eye movement, sound or sensation, I use EMDR in session in a more specific and targeted way to process traumatic memories moving it from subjective
(oftentimes disturbing) memory to objective memory.

EMDR is not hypnosis. Clients typically do not forget the trauma, but are less impaired by the effects of it.