There are two different versions about Ganesha’s birth. One has it that Goddess Parvati created Ganesha out of dirt off her body while having a bath and set him to guard her door while she finishes her bath. Shiva who has gone out, returned at that time, but as Ganesha didn’t know of him, stopped him from entering. An angry Shiva severed the head of Ganesha after a combat between the two. Parvati was enraged and Shiva promised Ganesha will live again. The devas who went in search of a head facing north of a dead person 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 legend has it that Ganesha was created by Shiva and Parvati on request of the Devas, to be a vighnakartaa (obstacle-creator) in the path of rakshasas (demonic beings), and a vighnahartaa (obstacle-averter) to help the Devas.
This year, September 17th marks the beginning of this festival which is also called as Vinayaka Chaturthi