Vajradhara is the ultimate primordial Buddha

Buddhahood

In Buddhism, buddhahood is the state of perfect enlightenment attained by a buddha .In Buddhism, the term buddha usually refers to one who has become enlightened...

, or Adi Buddha, according to the Gelug

Gelug

The Gelug or Gelug-pa , also known as the Yellow Hat sect, is a school of Buddhism founded by Je Tsongkhapa , a philosopher and Tibetan religious leader...

 and Kagyu

Kagyu

The Kagyu, Kagyupa, or Kagyud school, also known as the "Oral Lineage" or Whispered Transmission school, is today regarded as one of six main schools of Himalayan or Tibetan Buddhism, the other five being the Nyingma, Sakya, Jonang, Bon and Gelug...

 schools of Tibetan Buddhism

Tibetan Buddhism

Tibetan Buddhism is the body of Buddhist religious doctrine and institutions characteristic of Tibet and certain regions of the Himalayas, including northern Nepal, Bhutan, and India . It is the state religion of Bhutan...

.

In the evolution of Indian Buddhism, Vajradhara gradually displaced Samantabhadra

Samantabhadra

Samantabhadra , is a bodhisattva in Mahayana Buddhism associated with Buddhist practice and meditation. Together with Shakyamuni Buddha and fellow bodhisattva Manjusri he forms the Shakyamuni trinity in Buddhism...

, who remains the 'Primordial Buddha' in the Nyingma

Nyingma

The Nyingma tradition is the oldest of the four major schools of Tibetan Buddhism . "Nyingma" literally means "ancient," and is often referred to as Nga'gyur or the "old school" because it is founded on the first translations of Buddhist scriptures from Sanskrit into Tibetan, in the eighth century...

, or "Ancient School." However the two are metaphysically equivalent. Achieving the 'state of vajradhara' is synonymous with complete realisation.

According to the Kagyu lineage, Vajradhara is the primordial buddha, the dharmakaya

Dharmakaya

The Dharmakāya is a central idea in Mahayana Buddhism forming part of the Trikaya doctrine that was possibly first expounded in the Aṣṭasāhasrikā prajñā-pāramitā , composed in the 1st century BCE...

 buddha.