Raksha is the basic spirit with which the festival Rakshabandhan is celebrated in India. In this festival, a sister ties a string, known as Rakhi, around the wrist of her brother, asking him to protect her. The brother reciprocates by gifting his sister a present and renewing his vow to protect her.
Rakshabandhan is considered to be a festival that ties two people. A girl can tie a rakhi to a person who is not even her brother but the rule is that she has to continue tying it all her life. It is so because once a brother, always a brother. You cannot just tie it once and forget about it because when you become brother and sister, the relationship lasts forever.