A terton is a revealer of terma, the treasure-teachings held to have been concealed by Padmasambhava and Yeshe Tsogyal to be recovered when the time is right, chiefly in the Nyingma school.
The treasure tradition
The Nyingma tradition holds that Padmasambhava, who brought tantric Buddhism to Tibet, and his consort Yeshe Tsogyal concealed teachings, texts and sacred objects, the terma or treasures, in the land, in the mind, and in the elements, to be discovered in later ages by predestined revealers when those teachings would be most needed, and the terton is the one who recovers them, being understood as a reincarnation of a disciple of Padmasambhava entrusted with the particular treasure. The terton thus renews the tradition by bringing forth teachings held to originate with its founder but hidden until their time.
Revelation and its reception
The terma may be a physical object or text drawn from a place of concealment, or a teaching that arises directly in the mind of the terton, and the discovery of authentic treasures has been a major means by which the Nyingma tradition has been renewed across the centuries, with great tertons founding important lineages and cycles of practice. The claim to reveal a treasure is significant and has been subject to the tradition own scrutiny, since the authenticity of a terma and of the terton who reveals it is a matter of consequence. The office is not conferred but recognised, resting on the identification of the person as a destined revealer and on the reception of the treasures they bring forth. The terton thus represents a distinctive Tibetan mode of continuing revelation within an established tradition.