The Sanskrit word Upanayanam is made of Upa and Nayanam (vision through knowledge). Literally, it is identified as the second vision known as Wisdom & knowledge. Also, Dwijan as we call the boy to whom the ceremony is being performed, is known to get the second birth – first being born on the earth with physical body and second being “taking one near to wisdom” through this ceremony.
Essentially it has two parts. First is the investiture of the three stranded thread called Yagnopaveetha Dharanam. The second part is the Brahmopadesham – taking one to the Brahmman – a recitation into his right ear the Gayathri Mantra. This is usually performed by his father, who becomes the Teacher known as Guru to the boy.