Let’s understand the words - Agama, Nigama and Tantra. These words can be little confusing sometime as they are interrelated but with slight difference.
First of all, it is important to mention that Shruti (reveled knowledge) considered as the highest knowledge. Shruti texts includes both Agamas and Nigamas. In general Vedas are accepted as highest truth or revealed knowledge. But, lets understand each of them.
Nigamas: The word Nigama is understood as highest truth, thus Vedas are known as Nigama. Even the sentences of command contained in Vedas are referred as Nigama. Nigama also means the final truth or conclusion after applying all logics to counter all the objections. However, in Tantric world when Shakti as a teacher reveals the knowledge to Shiva, that is also called Nigama. Thus, this word can be confusing, if it is used in Vedic or Tantric way.
Agamas: The word Agama means 'that which has come to (us)' as revealed knowledge, these texts are called manuals of divine worship. The Agamas neither accepts or rejects the Vedas, however Agamas use the revealed knowledge of Vedas (e.g. mantra) when applicable for appropriate practices. To understand Agama and Tantra, we need to dive little deeper.
There are three types of Agamas.
- Vaishanava Agamas – worship and regard Vishnu as the supreme
- Shaiva Agamas – worship and regard Shiva as the supreme
- Shakta Agamas – worship and regard Divine Mother (Shakti) as the supreme
Shaiva and Shakta traditions of Agama texts are primarily based on the conversation between Shiva and Shakti. Each one is taking a role as a teacher and student. So, it is said that when Shiva as a teacher, revealed the knowledge to Shakti, it is called Agama, but when Shakti as a teacher, revealed the knowledge to Shiva, it is called Nigama, and it is also referred as Tantra.
Tantra: Tantra is technically Shakta Agamas, which worships and regards the Divine Mother (Shakti) as supreme Godhead. Thus, it is a sub-system of Agamas, but also recognized as Nigama or conclusive highest knowledge of Agamas. It is important to mention that Agama and Tantra words are now used interchangeably, however it is important to know the real distinction.