significance of yagnopavit

Select City Bangalore Chennai Delhi - NCR Hyderabad Kolkata Mumbai Pune Ahmedabad Coimbatore Rameswaram Haridwar Srirangapatna Gokarna Trimbakeshwar Kashi Thirupullani Thirumanancheri Ujjain Indore Bhubaneswar Lucknow Visakhapatnam Alandi Others

Select Priest preference TamilTeluguKannadaHindiMarathiGujaratiBengaliMalayalamOdia

I would like to know about significance of yagnopavit, Kindly contact me soon.