It's like any event/experience that indicates a significant change in someone's life...16th birthday/ Graduating from university/ marriage / becoming an adult (a teenager>>>an adult). It doesn't have to be a formal event...it could be a simple activity like... Example: "His friends felt that drinking a beer for the first time was a rite of passage to him becoming a man". "Moving out of her parents' home was a rite of passage to her becoming a responsible woman." So it's like an activity that qualifies you to belong to a specific "group"/ "position" etc.

A "rite" is a ceremony of some sort. A "rite of passage" is something you do to advance in some way or to mark some change. There is usually no ceremony, though the "rite of passage" itself can be regarded by some to be an unofficial rite of sorts. Rites of passage can have trivial importance and be noticed by nobody. Different people use the term in different ways. In my opinion, rites of passage tend not to be competitive, are rarely difficult, and need not be ordeals. Looking back in hindsight, they are often remembered, fondly, as trivial. They do not have to be major events. Nor need they mark important changes in a person's life. As an example, suppose you attend a university in a cold place where there is a lot of snow and everybody who is physically able learns to ski. At such a place, learning to ski would be considered to be a rite of passage. I consider weddings to be "rites", not "rites of passage" because they are far from routine, and not everybody who wants to be married finds someone. However, asking someone out on a date for the very first time is a huge rite of passage. Saying "I love you" for the first time is a rite of passage.