Based on the traditional hindu system , a person's life is divided into four ashramas. A person spends his life in each one of the ashramas
Brahmcharya - The first 12 years of this stage a child is supposed just be a child i.e they can play and frolic around and be pampered by their parents . In the 12th year the child is sent to the gurukul to gain education under a learned master.
Grihashta - Once the student is done is with his learning , he is given two options , one is to take the house holders life or the other is to pick the ascetic life. Girhastha is the name given to the householders life.
Vanaprastha - After fullfilling their worldly duties and sending their kids off to gurukul , the husband and wife now pursue their own spiritual journeys , they set out separately in search of truth.
The shashtipurti celebration ( 60th bday celebration ) is when both the husband and wife return from their spiritual quests, they are now deemed as new people who have been reborn and so are remarried again as a part of the shashitpurti ceremony.
Sanyasa - Eventually the husband and wife renounce the worldly pleasures and settle down for a life of ascetism in the forest till they die.
Kashi Yatra is a ceremony that symbolizes the transition from brahmyacharya to grihastha ashrama. The groom says he has finished his education and now wants to take up a life of a ascetic and so he wants to head to Kashi . The brides father or brother then convince the groom by telling about the qualities of their daughter and advising him as to how a householders life is going to benefit him.