Both pathologies consist of the presence of ectopic endometrial tissue, that is, outside its physiological location: the endometrium.
However, a distinction must be made between internal endometriosis or adenomyosis and external endometriosis. In the former, the endometrial tissue is found in the myometrium. In the second, it can appear in any organ of the body other than the uterus.
Generally, when we refer only to endometriosis, we are talking about external endometriosis.
On the other hand, it is also important to note that, although they are not exactly the same pathology, some women can present both at the same time.