An auspicious day dedicated to Lord Ganesha. On this day, the devotees observe strict fast. They break the fast at night after having darshan/auspicious sight of the moon preceded by prayers to Lord Ganesha.
The benefits of Chaturthi fasting include material progress, happiness and fulfillment of desires. The importance of Chaturthi vrat was explained by Lord Krishna to Yudhishtira, the eldest of the Pandavas. It is also mentioned in the Narasimha Purana and Bhavishaya Purana.
It is a very auspicious day to perform Ganapathi pooja or Ganapathi homam on this particular day.