This is  powerful thread worn by the Hindus. In the case of small children, it is usually tied around their waist and adults tie it in their left wrists or armlet. Some also tie a special root along with it and wear it as a necklace. People who practice black magic/Tantric vidhya may wear in their right foot as well.

Significance:

Green is the verdant color of nature and the environment, the  symbolism is health, youth, fertility, renewal, good luck and money.   Green is the color of the fourth or heart chakra.

Gold is the color meaning of wealth and endurance. Gold is symbolic of empires and kingdoms and reigns of power. The energy of the sun and the Lion, Gold is the color of confidence and courage

It is said to keep You and your  children away from evil eye (buri nazar).

It also keeps away people from evil spirit or unwanted tantra mantra done.