Santhara, or Sallekhana, is an ancient Jainist practice of embracing death. It is a slow process of withdrawal from outer life, beginning with fasting one day a week, then every other day, then giving up various foods, finally all food. Then one gives up water gradually, and finally one waits.
Sallekhana (also Santhara, Samadhi-marana, Samnyasa-marana) is a Jain practise of voluntary death through fasting when the end of life is very near due to unavoidable circumstances, such as illness or old age. It is the act of calmly withdrawing from worldly preoccupations and attachments by a combination of meditation and abstaining from food and water. In accepting to do sallekhana, the person must take a special vow to ensure that the body and the soul will leave the world in harmony and complete peace of mind, without fear. The purpose is to purge old karmas and prevent the creation of new ones.
This is from an article called Sallekhana in Jainworld.com, by Justic T. K. Tukol, L.D. Institute. This is Lessons for Seniors(15)
Sallekhana vs. suicide
Like most Dharmic religious traditions, Jainism considers suicide a wrong that only retains the karma from the current life and does not allow escape from the cycle of births and rebirths. Suicide involves an intentional act of harm against oneself with a known outcome that negatively affects those left behind. With Sallekhana, death is welcomed through a peaceful, tranquil process providing peace of mind for everyone involved.