http://en.wikipedia.org/wiki/Terma_%28Buddhism%29#Tert.C3.B6n
Terma (Wylie: gter ma) are key Tibetan Buddhist and Bön teachings, which the tradition holds were originally esoterically hidden by various adepts such as Padmasambhava and his consorts in the 8th century for future discovery at auspicious times by other adepts, known as tertöns. As such, they represent a tradition of continuing revelation in Buddhism[citation needed]. The majority of terma teachings are tantric in nature, although there are notable exceptions.
Tradition holds that terma may be a physical object such as a text or ritual implement that is buried in the ground (or earth), hidden in a rock or crystal, secreted in a herb, or a tree, hidden in a lake (or water), or hidden in the sky (space). Though a literal understanding of terma is "hidden treasure", and sometimes objects are hidden away, the teachings associated should be understood as being 'concealed within the mind of the guru', that is, the true place of concealment is in the terton's mindstream. If the concealed or encoded teaching or object is a text, it is often written in dakini script: a non-human type of code or writing.
http://en.wikipedia.org/wiki/Tert%C3%B6n
A tertön (Wylie: gter ston) is a discoverer of ancient texts or, one who finds terma. Many tertöns are considered incarnations of the 25 main disciples of Padmasambhava. A vast system of transmission lineages developed. Nyingma scriptures were updated by terma discoveries and terma teachings have guided many Buddhist and Bön practitioners.
