These are the methods of training and practice to attain the wisdom of Nirvana.
In Japanese, they are called either “Shichika Sanjushichidohon” or “Sanjushichi Bodaibumpo.”
This teaching, consisting of seven kinds of systems and thirty-seven curricula, outlines the methods to be practiced in order to gain the sacred wisdom of enlightenment.
In the Agon Sutras taught by the Buddha, the scriptures describe the state of Nirvana, or enlightenment, as an attainable goal, reachable through diligent practice.
Furthermore, the actual ways of training and practice for the realization of Nirvana are methodically detailed in the Agon Sutras. These methods of training and practice, called the Seven Systems and Thirty-Seven Practices, consist of seven courses and thirty-seven subjects. Kiriyama Kancho refers to them as “The Seven Systems and Thirty-Seven Curricula for the Realization of Sacred Wisdom.”

It happens that most people knowledgable about Buddhism in fact know only Mahayana Buddhism, many actually unaware that such Buddhist sutras teaching the way to Nirvana even exist.

The following mention of this teaching is taken from the Kinti Sutta, sutra 103 of the Majjhima Nikaya of the Pali Canon:

The Buddha says:
“So, bhikkhus, these things I have taught you after directly knowing them- that is, the four
foundations of mindfulness, the four right kinds of striving, the four bases for spiritual power, the five faculties, the five powers, the seven enlightenment factors, the Noble Eightfold Path- in these things you should all train in concord, with mutual appreciation, without dispute.”

Abhidharma Buddhists organized the numerous practices taught in the early sutras into a classification they called the "Thirty-Seven Kinds of Practices for Attaining Nirvana" or the “Seven Systems and Thirty-Seven Practices Conducive to Enlightenment.” In Japanese, this classification is termed Shichika Sanjushichidohon.

The Four Foundations of Mindfulness (cattari satipatthanani) This has earlier been translated as the Four Fields of Mindfulness, and has also been called the Contemplation of the Four Fields of Mindfulness. These are four kinds of contemplation, or the four meditation techniques conducive to attaining Buddhahood. These are the four foundations of mindfulness of the body, mindfulness of the feelings, mindfulness of the mind and of mindfulness of phenomena.
In practice, one contemplates and meditates that:

1. the body is impure,
2. feelings are suffering,
3. the mind is impermanent,
4. phenomena are devoid of independent existence.

We contemplate and meditate on the notion that our body is impure. We contemplate and meditate on the notion that all our feelings are suffering. We contemplate and meditate on the notion that our minds are impermanent. We contemplate and meditate on the notion that all phenomena are devoid of self.

The Four Right Efforts (cattaro sammappadhanani) This has earlier been translated as the Four Right Kinds of Striving. These are the four practices of effort to eradicate evil, to produce good, to augment good, and to prevent evil.

The practice of effort to eradicate evil is to try to eliminate the evil that has already arisen. This effort of elimination must be repeated many times.
The practice of effort to produce good is to try to produce good that has not yet arisen.
The practice of effort to augment good is to try to increase and improve the good that has already arisen.
The practice of effort to prevent evil is to try to prevent the evil that has not yet occurred from arising.

The Four Bases of Spiritual Power (cattaro iddhipada) This has also been translated as the Four Bases of Transcendental Knowledge. These are the practice methods that endow one with divine siddhi, or psychic power.

The spiritual power of the concentration of will is the possession of unobstructed freedom in relation to the material world.
The spiritual power of the concentration of effort is the possession of unobstructed freedom in relation to karma.
The spiritual power of the concentration of mind is the possession of unobstructed freedom in relation to the spiritual (non-material) world.
The spiritual power of the concentration of investigation into the principle of reality is the power to enter into the highest dhyana through the attaining of ultimate wisdom.

The Five Faculties (panca-indriyani) The Five Faculties, or Five Roots, are the faculties of faith, effort, mindfulness, concentration and wisdom. A faculty is a developed capability or ability that can be used at will. The practices that produce the profound faculties leading to Nirvana are faith (in the Three Jewels, the Buddha, the Dharma and the Sangha), diligent effort, mindfulness, concentration (meditation), and wisdom.

The Five Powers (panca balani) The Five Powers are the powers of faith, effort, mindfulness, concentration, and wisdom (or the power of knowledge). These are the practices endowing us with the five highest powers to achieve Nirvana. The Five Powers have the same virtues as the Five Faculties, but amplified, the realization of these five excellent powers signifying a greater measure of advancement on the path. They can be viewed, therefore, as differing in degree but not in kind.

The Seven Factors of Enlightenment (satta bojjhanga) The Seven Factors of Enlightenment consist of investigation of the dharma, effort, joy, tranquility, detachment, concentration and mindfulness. These are the seven practices that lead to Nirvana.

The factor of investigation of the dharma means the practice of distinguishing the true doctrine from the false doctrine.
The factor of effort is the practice of diligently maintaining one's concentrated effort with no backsliding.
The factor of joy is the practice of rejoicing in the study and application of the true dharma.
The factor of tranquility is the practice of eliminating procrastination and sluggishness and attaining a state of brightness and relaxation in one's body and mind.
The factor of detachment is the practice of achieving balance and securing serenity of mind by divorcing it from bias, hatred and attachment. It is the practice of detaching one's thoughts from external objects.
The factor of concentration is the practice of attaining a concentrated mind, both in meditation and in daily life.
The factor of mindfulness is the practice of maintaining equilibrium of thought.

The Noble Eightfold Path (ariya-atthangika-magga) Right View: This is the correct view, the correct way of looking at things. This refers to the correct view of the world and of human nature according to Buddhism.
Right Thought: This is the correct way of thinking, the right mental attitude. Right thought is to always think correctly about one's situation, to decide on the best course.
Right speech: This refers to correct speaking, the activity of using correct language and speaking truth.
Right action: This refers to the correct activity of the physical body.
Right livelihood: This is the correct way of conducting our lives. Livelihood here means lifestyle or way of living.
Right effort: This is the correct striving, the right courage.
Right mindfulness: This refers to the correct awareness, the right consciousness and correct consideration.
Right concentration: This is the correct dhyana, or states of meditative absorption.
These seven systems and thirty-seven practices can be further divided into the categories of:

1. meditation
2. practice
3. tapas (intensive spiritual exercises).

The Four Foundations of Mindfulness and the Five Faculties belong to the category of meditation. The Four Right Efforts, the Five Powers, the Seven Factors of Enlightenment, and the Noble Eightfold Path fall into the categories of meditation and practice. The Four Bases of Spiritual Power belongs to the category of tapas, for the attainment of a level of spiritual power referred to as divine siddhi, or supernatural power. The Four Bases of Spiritual Power teach four practices for the development of supernatural power.