Tihar or the festival of light is the second biggest festival of Nepal (among Hindus) after dashain, which lasts for 5 days. Personally I find this festival more interesting and exciting. Walking around the city has another charm, people busy trying to decorate their houses, shops with garlands, lights, small kids firing crackers.
The illustrated image is of Diya (made of soil) and oil is used to burn the threads (we call it eta in Newari). Diya is traditional form of decorating houses however these days people use candles, colored bulbs, small animating lights. The motive is to decorate the house as much as possible to attract Laxmi, the goddess of Wealth. Is there such goddess? Well if there had been, Nepal wouldn't be among the least developed countries. The funny thing is our donors are Laxmi, why don't we pray to our donors and stick their photos in our houses instead of Laxmi. Anyways tradition is tradition. Shutup and see if Laxmi has come to your house. And keep the door open. Also keep your eyes and ears open to separate theives from Laxmi ;-)