What is the practice of "suttee" as noted in the memoir, The Year of Magical Thinking?

The process of "suttee" was a common practice in India for centuries. The wife of a dead man was herself burned to death on a flaming boat. The author comments in chapter five part two that the practice might not be as barbaric as it sounds—she suggests that for the women, the fire was "an accurate representation of the place to which their grief had taken them".