Nagarjuna is venerated by all sects and schools of Mahayana Buddhism for his ancient commentaries on the Buddha’s teachings, so such so that he’s often referred to as the Second Buddha.
Nagarjuna is perhaps most well-known for his distinction between relative truth and Ultimate Truth, which he likened to a finger pointing at the moon:
The highest truth (paramarthasatya) is beyond words or description, i.e. beyond the reach of conceptual understanding and yet it was presented by the Buddha Shakyamuni as his teaching so that our conceptual understanding could grasp it. It is in this sense that the teaching is regarded as an ‘expedient means’ (upaya), often likened to a finger pointing to the moon. What is crucial about this metaphor is that the finger and the moon are mutually reflexive. Without the finger, the moon would not be known. Without the moon, there would be no need for the finger pointing to it.
Nagarjuna was also the first patriarch of Pure Land Buddhism, the first commentator to endorse Pure Land practice as the easy path to Buddhahood:
The bodhisattva Nagarjuna emphasizes this core teaching of Pure Land Buddhism, saying in Chapter on the Easy Path, “Amitabha’s Fundamental Vow is as follows: If anyone invokes me, recites my name (Namu-Amida-Butsu), and takes Refuge in me, he will instantly enter the state of assurance (of future Buddhahood), and subsequently attain the highest perfect enlightenment. For that reason, you should always be mindful of him.”
From the perspective of two-truths doctrine, the stories of Amida in the Pure Land scriptures and even the recitation of his name are a relative truth, a symbolic expression for enabling us to realize the Ultimate Truth of Dharma-body:
Buddha exists in many forms, but all share the same “body of reality,” the same Dharmakaya, which is formless, omnipresent, all-pervading, indescribable, infinite–the everywhere-equal essence of all things, the one reality within-and-beyond all appearances.
Dharmakaya Buddha is utterly abstract and in fact inconceivable, so buddha takes on particular forms to communicate with living beings by coming within their range of perception. For most people, this is the only way that buddha can become comprehensible and of practical use. The particular embodiments of buddha, known as Nirmanakaya, are supreme examples of compassionate skill-in-means (upaya).