The Yagnopaveetham is a triple stranded sacred thread that is worn by those initiated into the Gayatri recital. The three strands represent the three sandhya rites that are to be performed when the sun rises, when the sun is at its zenith and when the sun sets. The rites are in adoration of the Hindu trinity (Trimurti): Brahma, Vishnu, and Shiva. The purpose of the rites is to invoke God to bless the initiated seeker to lead a good life at all times (past, present, and future), in all planes or regions (heaven, earth and netherworld).
The bearer of the yagnopaveetham is supposed to be engaged in the study of at least one Veda, with each strand representing one of the three Vedas, namely the Rig, Yajur and Saama Vedas of the Trayi Veda system (Atharva Veda was not included in the Trayi Veda system when it was in vogue).
A Brahmachari - vatu - wears one triple stranded sacred thread. In ancient times women also wore such sacred threads and performed sandhya rites. During subsequent periods, a married woman's privilege or responsibility of performing such rites was transferred to her husband. Since then, each married man has been expected to wear a pair of triple stranded sacred threads, one for himself and another representing that of his spouse. Thus he is expected to perform sandhya rites on behalf of both and share the benefits with his spouse.