The most important puja performed on Diwali is the Lakshmi Puja dedicated to the Hindu Goddess of prosperity, luck and wealth. But why do we perform Lakshmi Puja especially on Diwali day. Legend has it that Goddess Lakshmi incarnated on Diwali day during the legendary churning of ocean (samudra-manthan) in the Puranas. This is the main reason why Lakshmi Puja is performed on Diwali.
Another legend has it that on Diwali day, Lord Vishnu in his fifth incarnation as Vaman Avatar rescued Goddess Lakshmi from the prison of King Bali.
People perform Lakshmi Puja on the day for peace, prosperity, material wealth and spiritual wealth.
The popular belief is that Goddess Lakshmi visits homes on the day and she is welcomed by keeping the premises clean and neat.