Ganesh Chathurti is a festival celebrating the elephant headed god Ganesh. Ganesh is the youngest son of Lord Shiva and Parvati and appears during the fourth day of the Hindu lunar-solar calendar in the month of Badrapada (August/September)

There are two stories of his appearance. One says, that the Goddess Parvati created Ganesha out of mud to guard her bathing area. Shiva was away during this time and when he returned Ganesh stopped him from entering. An angry Shiva severed the head of Ganesha during combat. Parvati was enraged and Shiva promised Ganesha will live again. The devas who went in search of a head could manage only the head of an elephant. Shiva fixed the elephant’s head on the child and brought him back to life.

The other story of  the appearance of Ganesha is that he was created by Shiva and Parvati on request of the Devas (gods), to be a vighnakartaa (obstacle-creator) in the path of rakshasas (demons). His devotees worship him as the remover of obstacles.
Lord Ganesh is also the scribe for the great epic Mahabharata, narrated by Vyasadev.
Lord Ganesh is favoured by many Hindus. Images of Ganesh would be at the entrance of homes and on home alters.
How is this festival celebrated?
Hindus all around the world celebrate this festival, more so India where it is celebrated over 10 days. Temporary shrines of Ganesh are constructed. Special pujas (prayers) are performed asking Ganesh to reside with the temporary created forms. Many sweets, coconuts and flowers are offered to Lord Ganesh and lots of chanting of his names to invoke auspiciousness. It all culminates in Ganesh being taken to a river or sea to be submerged in the waters.