The Vedas recognized four stages of life (or ashramas) that the average human being went through. While some of these stages appear to be culturally specific and irrelevant to modern life, on closer examination they actually describe common transitions that most people go through in all societies.
This is the life of a student, followed by the very young. In this stage, the individual is learning not just how to make a living but also how to be a thoughtful human being. For a brahmachari, education must be the first priority. Thus, students are encouraged to live simple, celibate lives without excessive indulgence of any kind and without assuming responsibility for the care of other human beings. Such responsibilities come at a later stage.
This is the life of a householder, of someone who has completed his or her education and is now earning a living or running a household or both. This person has responsibilities not only to himself or herself, but also to those under his or her care. For example, someone in grihasthashrama may have responsibilities to children, to a spouse, to clients, to an employer, to neighbors, to aged parents and other relatives and to others as well. This is the busiest and most materially productive stage of a human life.
Literally, this means the stage of one's life when one goes to the forest. In a general sense, however, vanaprastha is a period of retirement. When one has given up one's regular employment, when one's children and other dependents no longer need support, then one can devote oneself to a quiet life of contemplation. In early Indian society, this often meant leaving the home and the village and going to live in the forest with one's spouse. In vanaprastha, husband and wife still live together, though generally without regular intimate relations. They still maintain regular contact with their offspring and other relatives, but they are no longer responsible for them. The point of vanaprastha is to lead a serene and reflective life without responsibilities, dependents, excessive stress or excessive indulgence.
Sanyaasa is the final stage, and an optional one-it is less common than the first three stages. Sanyaasa means renunciation of all earthly ties and burdens and dedicating the rest of one's life spiritual and philosophical growth. In sanyaasa, even marital and family ties are dissolved. Individuals live by themselves (in Vedic society, sanyaasa generally involved living in the forest, as vanaprastha did) and spend their final days in contemplation and meditation.