Tantra (rgyud, Kontinuum) Is a complex system in tibetan Buddhism, which is described in the Anuttarayoga Tantra with the help of a twilight language.
The expression is mentioned for the first time in the Guhyasamāja: 'Tantra is called continuity, and the tantra is divided into three aspects: Ground together with its nature and indispensability. Nature is the fundamental cause, the soil is the method, and the result is indispensable. The meaning of tantra is contained in these three. '
The teachings of the tantra have here an external, an inner and a secret meaning.
The qualities, that are overcome by the sadhana of a particular divinity, often appear symbolically as attributes of this deity. An example ist the Srī-guhyasarvacchinda-tantrarāja
Traditionally, higher tantras require an empowerment and a transmission from a qualified Guru or Lama before they are studied and practiced. As a rule, they were not publicly discussed.
The tantric techniques of Mahayoga, Anuyoga and Atiyoga (Dzogchen) build on each other.
Anuttarayoga Tantra (Wylie-Tibetan: bla na med pa'i rgyud, "Unrivaled Yoga Tantra" or "Highest Yoga Tantra") is a term from Tibetan Buddhism in the category of 'esoteric tantra' (Vajrayana) in the Buddhist texts, which form a part of the Kangyur ("translated words of the Buddha") in the Buddhist canon. It was also handed over in the Gyu De Kun Tus.
The three big tibetan lines of the "period of the new translation" (Sarma) divide tantra into four classes:
In the Sarma schools of Tibetan Buddhism, the Anuttarayoga tantra is the highest of four classes and is associated with the Mahamudra (Tibetan phyag-chen) path to enlightenment.
According to Gelug tradition, the Buddha taught in the 'Highest Yoga Tantra' the most profound instructions for the transformation of sensual pleasure into the fast path to enlightenment, which, on the other hand, depends on the ability to collect the inner winds(tibet.: rlung; Sanskrit : prana) in the central channel and dissolve them by the power of meditation.
In the classification of the Dzogchen system (Tibetan: rdzogs-chen, "great perfection") of the Nyingmapa, it is regarded as equal to the Mahayoga tantras, the first of inner tantras.
The Dalai Lama noted: "The old translation Dzogchen and the new translation of the Anuttarayoga Tantra offer equivalent paths which bring practitioners to the same state of Buddhahood." 
The practice of Anuttarayoga tantra in the Vajrayana tradition is characterized by the requirement of empowerment by a qualified lama, as well as the use of ritual techniques and the practice of various meditative and subtle yogas to effect personal transformation and enlightenment through the realization of the 'moment-to-moment continuity' of consciousness (Sanskrit: citta-samtāna) of a meditation deity (that is, a Sambhogakaya form of realized beings) or a yidam. 
According to Miranda Shaw, Anuttarayoga Tantra texts have remained at the forefront of contemplation, ritual, and interpretation in the Tibetan Buddhist area .
Anuttarayoga-Tantra literally means ' unsurpassed unity continuum'. Although the term is often translated as 'Highest Yoga Tantra' in English, this is not very accurate.
The tibetan expression bla med (translated back into Sanskrit as anuttara) is a negation of a 'relatively-not' or 'nothing'(med/an) higher (bla/uttara) - rather than a superlative. If the authors of this term had intended to indicate directly 'the highest', other superlatives would have been available, for example mchog ("highest" or Sanskrit: uttama "supreme").
Instead, they consistently choose a comparison rather than a superlative. Similarly, the terms used in Sanskrit use uniform comparisons: yogottara ("higher than yoga") and niruttara (a negation of the comparative value). This nuance has been generally overlooked in English and European translations.
As a scholar, Isabelle Onians explained: "Yogini-Tantras are called anuttarayoga in the secondary literature. But this is based on an erroneous back-translation of the Tibetan translation (rnal byor bla med kyi rgyud), which only appear as Yogānuttara or Yoganiruttara in the Sanskrit texts. "
== Anuttarayoga in tibetan classification ==
The expression appears in the 'Five Groups of the Dharma' with reference to Geshe Pabongka Rinpoche . They contain:
In the above Sarma schools of tibetan Buddhism, the four categories of Tantra are also Kriyā-Tantra, Caryā-Tantra, Yoga-Tantra and Anuttarayoga-Tantra.
Another subdivision within the Anuttarayoga tantras is sometimes performed in 'father' (Yamantaka and Guhyasamaja), 'mother' (Chakrasamvara and Hevajra) and 'nondual' tantras (Hevajra and Kalachakra), although the latter category is under discussion.
In the Nyingma schools of Tibetan Buddhism, the Anuttarayoga tantra is sometimes used as a synonym for the Mahāyoga tantra of the Nyingma nine-yāna ('vehicle') formulation, in which six planes are articulated in two triads, the 'outer' and the 'inner' 'Tantras. The outer tantras are Kriyā-Tantra, Caryā-Tantra and Yoga-Tantra. The inner tantras are Mahāyoga, Anuyoga and Atiyoga (Dzogchen).
Sorts of Anuttarayoga-Tantras
Five types of anuttarayoga tantras were initially popular in Tibet: Guhyasamaja ("Esoteric Community"), Yamāntaka ("Vajra"), Hevajra ("O, Vajra!"), Mahāmāyā ("Great Game of Illusion") and Chakrasamvara (" Wheel of Great Bliss ").
The Kalachakra ("Wheel of Time") - Tantra was spread somewhat later. To date, the term 'Anuttarayoga Tantra' has not been discovered in Indian sources, including the categories used, the 'Mahāyoga' and the 'Yogottara', the 'Yoganiruttara' or 'Yoginī-Tantras', which the tibetans call "father" (Tib .: pha rgyud) and "mother" tantras (tib .: ma rgyud).
The 'Mahāyoga Tantras' of the Indian Pala Dynasty were known in Tibet as 'Father Tantras'.
Following the conclusions of Tsongkhapas (Gelug), father Tantras emphasize the creation of a Buddha - form by cultivating a gyulu or illusion - body (tib .: sgyu-lus, Sanskrit: māyākāyā, chinese: mahādeha) on the basis of practices with the rlung- Energy system of the subtle body.
Earlier Sakya masters and Kagyu scholars had regarded father Tantras as the practice of blissful consciousness. 
Father tantras also use the anger (pratigha) as an exercise on the path of practice, focusing on the 'emptiness' aspect of Buddha nature.
The post-Tsongkhapa Sakya scholar Tagtshang Lotsawa identified father-tantras as those who emphasize the secret or hidden empowerment of the four empowerments (tibetan: wang, Sanskrit: abhisheka) of the Anuttarayoga tantra.
The secret empowerment plants the seeds to obtain an illusion body. By visualizing all phenomena as the divinities of the mandala of the Buddhas, all phenomena are purified in the development stage.
Among the father tantras are the Guhyasamâja and also the Yamantaka and the practices of the 'illusion body' and the dream yoga.
Father-tantras refer to the phase of the generation (Kyerim) of the meditative transformation.
The "yoginī tantras", which became known in Tibet as "mother tantras" (tib .: ma-rgyud), emphasize the development of enlightened consciousness (the "gyulu" spirit) through the cultivation of the fundamentally pure mind of all beings, known as 'splendor' or 'osel' (tibetan od-gsal, Sanskrit: prabhashvara) or 'clear light').
They focus on devotion as the basis of Vajrayana practice.  They are also based on the use of desire (trsnā) as the path of practice, focusing on the radiant (prabhāshvara) aspect of the buddha - nature.
Among the mother tantras, the most famous is the Chakrasamvara ("The Wheel of the Highest Bliss").  The practice of the Vajrayogini developed from the Chakrasamvara and is today an independent de facto practice with about twelve complete sadhanas or instructions for pictorial meditation. 
Other mother-tantras are Hevajra-Tantra and Caṇḍamahāroṇaṇa-Tantra. Hither also belong the Tummo and the Hevajra.
Mother Tantras refer to the phase of completion, and nondual tantras combine both: the generation phase (Kyerim) and the completion phase (Dzogrim).
== Nondual Tantras ==
Nondual tantras use both anger and desire as a counterpart to deception (Avidya) and focus on both the physical and the mental, the empty and radiant aspects of the enlightened mind.
The best example for this category is the Kalachakra, next to Vajrakilaya and Hevajra 
The Sakya tradition also considers the Hevajra as nondual tantra, but other traditions classify it as 'yoginī-tantra'.
In the "deity yoga" (tha .: lha'i rnal 'byor) - practices of the Anuttarayoga tantra, two stages are practiced: the generation stage (Kyerim) and the completion stage (Dzogrim). 
In some tantras, both steps are practiced side by side.
In others the 'stage of production', in which the practitioner is still working with the imagination, must be completed before the beginning of the practice of the 'completion stage'.
The meditator, who has recognized the emptiness, runs through the mind the whole cycle of life of death, bardo, and rebirth.
The final state involves the generation in the form of deities. The goal is to control the types of consciousness and the '8 consciousness layers' up to the 'clear light' and the conditions that accompany them.
Der Endzustand beinhaltet die Erzeugung in Form von Gottheiten. Das Ziel ist die Kontrolle über die Bewusstseinsarten und die '8 Bewusstseinsschichten' bis zum 'klaren Licht' und der mit ihnen einhergehenden Bedingungen.