The Republic Day in India marks the date on which India had officially adapted the constitution, thereby becoming a republic.
A republic is a form of government where the power lies with the people and their elected representatives.
India became a republic on January 26, 1950, when it formally adopted the constitution as the legal framework of how the country would work. A national holiday is observed on this day.
Every year on Republic day is celebrated in Rajpath, Delhi. There are parades in front of the President to mark the day of celebration.