I have experienced it on several occasions and with 2 different practitioners - 1 male and 1 female.
It was discovered by a psychotherapist (I think) in the US called Shapiro. She noticed while walking her dogs that if you used the rapid eye movements that occur naturally while dreaming while thinhking about a distressing or traumatising past event in your life it helps reduce the itensity of the memory, and eventually it just becomes something that happened in the past.
I suffered from ptsd relating to being sexually abused as a child and being bullied by my mother to the extent of having an unsuccessful attempt at suicide when I was 16.
With ptsd, the event doesn't get dealt with and keeps coming up to the surface all the time, without often any trigger occurring. EMDR helps file it away in its proper place like anything else you may have done, say 10 years ago.
Can recommend it, however, for anyone having it for the first time, you can be very 'open' to external stimuli afterwards. I went to see the file Babe the night after and all the closeups of faces triggered something from my past, and I ran home and ended up in a screaming heap under the kitchen table.
I have since managed to come out.
There is an emdr site that lists all practitioners and the level of qualification that they have.
Good luck