This was Siddhartha Gautama's mom dreaming about a white elephant that meant that her son was renouncer.
Despite not being allowed to leave his home Siddhartha Gautama eventually snuck out, isolating himself from the riches his family had.
From his walks, Siddhartha Gautama saw the three types of suffering of man (Growing old, sickness, and death). From that Siddhartha Gautama come up with a philosophy this was the three types of suffering
From there Siddhartha Gautama mediated under a tree for a long time and achieved enlightenment then showed his teaching and spread it across Asia from his missionaries.
Buddhism believed in reincarnation, which was determined by the dead person's karma. But Buddhism did not believe in hierarchy.
Buddhism spread throughout Asia through his missionaries. And till this day Buddhism is an important part in many cultures.