What the difference is betwen endometritis and endometriosis?

Its different. Endometritis is an infection of the lining of the uterus ( endometrium) that can occur following prolonged labor or cs as well as uterine instrumentation eg: d&c, hysteroscopy. It can also be caused by stds. Endometriosis is a chronic condition, where the hormone- responsive endometrial tissue grow outside the uterine cavity, mostly on the peritoneal cavity or within the ovaries.
One is infection. Endometritis is an infection of the inner uterine lining. Endometriosis is a chronic inflammatory condition resulting from endometrial like tissue in the pelvis that can cause pain and infertility.