Govardhan Puja is also known as the Annakut puja meaning a pile of grains. It is celebrated to commemorate the lifting of Mount Govardhan by lord Krishna.
According to a legend in Vishnu Puran, before Lord Krishna was born, Lord Indra, the god of rain, was the chief deity of Vraj. Lord Krishna instigated the people to stop worshiping Indra. Indra wanted to prove his power over Krishna so he brought about a cloud-burst which flooded the area for many days. People were afraid that the downpour was a result of Lord Indras wrath. That was when Krishna came forward and lifted Mount Govardhan as an umbrella on the little finger of his right hand so that everyone could take shelter from the rain. Its because of this incident that he got the epithet Govardhandhari.