Indian festivals are, more often than not, larger than life. 
Traditioanlly, Lohri Festival celebrates the onset of the harvest season in Punjab. People celebrate on this day to offer thanks to god for the precious crops before they begin harvesting them. 
People build a community bonfire and everyone gathers around it. This is the cynosure of this festival.
Offerings are fed to the fire to appease the gods and to ask them to bless everybody  with abundance and prosperity.