Here are some quotes from the U.S. Grand Lodge website:

Ordo Templi Orientis is the first of the great Old Æon orders to accept The Book of the Law, received by Aleister Crowley in 1904 EV. This book proclaims a New Æon in human thought, culture and religion. The Æon arises from a single supreme injunction: the Law of Thelema, which is Do what thou wilt.

The letters O.T.O. stand for Ordo Templi Orientis, the Order of Oriental Templars, or Order of the Temple of the East. O.T.O. is dedicated to the high purpose of securing the Liberty of the Individual and his or her advancement in Light, Wisdom, Understanding, Knowledge, and Power through Beauty, Courage, and Wit, on the Foundation of Universal Brotherhood.

The United States Grand Lodge website offers an excellent history of O.T.O., and you are encouraged to make use of that resource.

Here at Bubastis Oasis we offer initiation into the Minerval, and the first three degrees of Ordo Templi Orientis. If you are interested in joining the Order, please speak with a body officer.