"protection", and Bandhan means "to tie".
Traditionally, during the festival a sister would tie a rakhi, a bracelet made of interwoven red and gold threads, around her brother's wrists to celebrate their relationship.
In modern days priests tie rakhis around the wrists of congregation members. Close friends also share rakhis, and women would even tie rakhis around the wrists of the prime minister.
It is believed that when a woman ties a rakhi around the hand of a man, then the man is compelled to protect her for a year as part of his religious duty.
Rakhis are traditionally tied by people familiar with the Vedas (the Hindu holy scripts). As the rakhi is tied, the woman offers a prayer asking for happiness and prosperity. Once the rakhi has been tied a mantra is chanted either in Sanskrit or Punjabi.
At the end of the ceremony the sister places a sweet in her mouth, and her brother gives her a small monetary gift of appreciation.
The rakhi is believed to remove sin from one hand and provide safety to the other.