This photo was taken at Vrindavan, Uttar Pradesh.
Janeu is worn both by bachelors as well as married men.
Three thread Janeu is worn by bachelors (à¤¬à¥à¤°à¤¹à¥à¤®à¤šà¤¾à¤°à¥€) and Six thread (3 for Husband+3 for Wife = 6) is worn by married men.
(Knowledge shared and enhanced by Shiv Dayal and Ram Krishna – my friends from Vrindavan)
For more details one can read Manusmriti.
Benefits of wearing Janeu (in Hindi)