Upanayanam is a sacred thread ceremony meant for boys after they attain the age of 8. But sometimes, it is lingered and celebrated before the marriage.
It is the wearing of a sacred thread that is to be worn till his death. The person gets entitled to receive enlightened spiritual education and other privileges to perform sacred rituals only on wearing this thread that is called as “yajnopavita”. The thread is worn after purifying it through the chanting of mantras and performance of some rituals by his parents.