"Essenes ("Judah" in some Qumran writings) were members of one of the three orders of Jews during the Second Temple Period; a separatist group that formed an ascetic monastic community and, in response to apocalyptic visions, retreated to the wilderness."
-Library of Congress
The Essenes came to international attention with the discovery of the Dead Sea scrolls in a Qumran cave. Later, more caves, and more scrolls were found. These scrolls are thought to represent the Essenes or to have been written by them around the turn of the eras. The Dead Sea scrolls include the Biblical and secular texts.
Josephus wrote about the Essenes as one of 3 Jewish sects in the Second Temple Period. Besides the Essenes, Josephus lists the Sadducees and the Pharisees. The Essenes, he writes, are virtuous, generally continent, using adoption as the preferred means of acquiring children. They recite prayers and engage in purification rituals and are also gifted with prophecy. Pliny the Elder also mentions the Essenes, as a Jewish group living north of the Dead Sea. Philo mentions the Essaeens as a celibate, virtuous people who lived communality and spent their lives studying ethics and ancestral law.
Excavations have found evidence of what may have been the Essene monastery's latrine. See More on the Dead Sea Scrolls and the Essenes' Toilet.
Reference: The Dead Sea Scrolls: A Biography, by John J. Collins; Princeton University Press: 2012.