Ganesh is the son of Godess Parvathi Devi and Lord Shiva. He is the only god who makes the whole world get rid of obstacles and from halfwit. The story behind his birth is after skhira sagara mdhanam Lord Shiva goes to meditation for long period, so in his absence the world gets edicted to halfwit and many unfortune and evil things happen, so all other gods come to Parvathi Devi and asks her to give birth to a child who makes all unfortune things fortune and all sins become boons by just looking at him. According to the request maa Parvathi makes an idol thinking about Shiva with the paste(made of turmeric, mung dal etc used to clean the body while taking bath) taken from her body after that with mantras and her shakthi she gives life to that idol and names him as "Vinayaka". After long tapas/meditation Shiva will be returning to kailas and this news will be known by Parvathi Devi so she thinks to get ready for his arrival and thought to get freshen up and do pooja before Lord Shiva returns to kailas but in middle Nandi and remaining gana's will stop her questioning what to get for pooja etc, she then tells Vinayaka to stand infront of her ekantha room and not let anyone come inside till her pooja gets finished and gives him vundrallu (laddus at north side) to eat and a weapon to protect himself (laddus at north side).
Shiva returns to kailas (he already knows about vinayaka without his wish maa Parvathi will not do any thing) he comes to meet Parvathi Devi but the small boy infront of the gate doesn't let him go inside Shiva tries to make him understand that he is his father and he is going to meet his wife but the boy doesn't listen to him and rudely tells him that he won't allow him. Lord Shiva leaves from there. Devendra, Nandi and some other gods come to take Vinayaka to Shiva but he doesn't listen to them and beats them rudely, they run to Lord Shiva with afraid and conveys their pain to him, then Lord Shiva gets angry on ill treatment of Vinayaka to remaining gods and he goes to him but he treats the same, then Shankara tells him this head weight of a person drags him to under ground and cuts his head with his trishulam (weapon).
After taking bath and performing pooja Parvathi Devi comes outside to see whether Shiva returned back and looks at the dead body of her son without head and comes to know of all that happened and he turns to Durga matha and strats destructing the whole world, then all other gods request Lord Shiva to calm down Parvathi Devi, he says only rebirth of Vinayaka makes her calm, so he sends Nandi and team towards east and tells them to bring the creature head of whom they see first, then Nandi goes long but he doesn't find any thing he gets disappointed, at that moment he sees an elephant there and goes to it. Then that elephant says to Nandi that he is happy that he got the time for moksha and continues telling him that he got a boon from Shankara that he will stay with him and he will be treated as god and tells them to do what ever they want he will support them. Nandi with super happy cuts the elephant head and returns to kailas, there lord Shiva attaches the head to the body of Vinayaka and lord Vishu gives him life.
Parvathi Devi is very fond and names him as "Gajanana" and makes him as first one to be treated among gods. Vinayaka is fond of vundrallu and he is the one with utmost samskaar and treats his parents with lots of respect. He is the origin to ultimate knowledge, he will be fond for simple rituals and so he is very happy with what he has so always he will be dancing (a person with troubles and sadness can never dance all the time).
Vinayaka gets married to Siddhi and Buddhi there is a wording that Siddhi and Buddhi are for knowledge but Vinayaka he himself is the origin to knowledge, so these to Siddhi and Buddhi came from himself.
On the auspicious day Badrapadha Chathurdhi comes between august and september Parvathi devi appoints vinayaka as the first god to be worshiped.
Ganesh is called as Vigneswarudu which means Lord of Vignas (Obstacles). Puranas say that we have to worship Lord Ganesh before starting any work, so that you will not get any obstacles in middle of the work and your work completed successfully.
