What is Lohri and why do punjabi people celebrate it?

Hi there, I'm a writer. I'm currently writing something that requires me having the base knowledge of what Lohri is and why is it celebrated? I did some research and came up with this: 1. It is a festival celebrated to mark the end of winter solstice or the end winter season in northern parts of India (up extreme north like punjab, Hp, Hr and others). 2. It includes lighting up the primal source of creation (Fire) to mark the end of long winter nights. Am I correct? Or am I wrong? Please native peeps, help me get the facts right.