Upanayana is a special ceremony that happens in Hindu culture when a boy is considered old enough to start learning about important things like religion and spirituality. It's like a big party where the boy gets dressed up in fancy clothes and gets a special haircut.
During the ceremony, the boy gets a special thread called a "sacred thread" that he wears over his shoulder for the rest of his life as a symbol of his spiritual journey. He also gets a special teacher called a "guru" who will help him learn about important things like meditation and prayer.
Overall, Upanayana is a very important ceremony in Hindu culture because it marks the beginning of a boy's journey to becoming a wise and spiritual person.