Sallekhana (also spelled salekhana or santhara) is a special Jain vow in which a person voluntarily prepares for death by gradually reducing food and water, while staying in complete peace, awareness, and detachment.

In simple words:

• Meaning:

“Sallekhana” means proper thinning of: - the body (kāya) and - the passions (kashāyas – anger, pride, deceit, greed). The main aim is to reduce attachment, hatred, fear, and desires, and to remember the soul’s true nature at the last moment.

• What it is (Jain view):

- A spiritual vow, taken calmly and publicly. - Usually done when: - life is naturally near its end (old age, incurable disease), or - further living would mean only suffering and more violence (himsa) through the body. - The person: - slowly reduces intake (not sudden stopping), - spends time in prarthana, samayik, pratikraman, jap, svadhyaya, - asks forgiveness from all, and stays in equanimity (samatā).

• Not considered suicide in Jain Dharma:

- Suicide is done out of despair, anger, fear, or attachment to an idea. - Sallekhana must be without passions – no desire to die quickly, no hatred of life, only acceptance of nature and focus on the soul. - No poison, weapons, or sudden violent means are allowed.

• Who can take it:

- Both monks/nuns and householders may take sallekhana, - Always under guidance of an experienced guru / Jain elder, - Only in rare and right conditions, not as a solution to normal problems.

• Digambar / Shvetambar view:

- Both traditions accept the principle of sallekhana as a high spiritual vow. - There may be differences in procedure and emphasis (how it is done step‑by‑step, specific rituals, wording of vows), but the core idea is the same: a peaceful, voluntary, dharmic end, with complete detachment and remembrance of the soul.

In essence, sallekhana is seen as:

• the final act of renunciation,
• a way to avoid new karma at death,
• and to die in samyak darshan–samyak jnān–samyak charitra as far as possible.

You can read a bit more in simple language here