"EMDR stands for Eye Movement Desensitization and Reprocessing. It is widely assumed that severe emotional pain requires a long time to heal. EMDR therapy shows that the mind can in fact heal from psychological trauma much as the body recovers from physical trauma.
A book I often recommend is "Getting Past Your Past" written by the creator of EMDR, Dr. Francine Sharpiro (2013). This gives a great overview of EMDR without the clinical jargon.
EMDR practitioners attend an intensive, specialized post-Masters training and supervision in order to provide this type of therapy. There are some websites that promote doing "self-EMDR" which not only is unethical, but is dangerous since EMDR requires that a highly skilled counselor work closely with you in order to ensure that you are not re-traumatized or experience adverse effects.