The literal meaning of the word Ganesha is lord of groups. He is the Lord (Isa) of the groups (Gana) of Shiva's attendants.
One legend recounts that Parvati scuff off her body, mixed it with oil, fashioned into a small child, and commended life into this figure by sprinkling Gangas water. This child was then asked to guard her bathroom door. When Shiva tried to enter and found his entrance denied, he cut off Ganesh's head following a battle. On seeing Parvati's sorrow, Shiva severed the head of the first living being, which happened to be the elephant, and joined to the child.
He is God of Wisdom, master of knowledge, champion of worldly achievements, and remover of obstacles. He is invoked at the beginning of all religious events, and many important undertakings. He is represented with four hands: two of them hold noose (Paasa) and goad (Ankush); other two are held in the position of protection-giving (Abhava) and blessing (Varada). These four hands represent four Vedas. He has only one tusk. He is said to have written down Mahabharat from the dictation of sage Vyasa. He is depicted as riding mouse (Mushak). Atma (self) is depicted as mouse. If not guarded, like mouse, self steals away all that other people possess. Ganesh is represented by sound image (mantra), AUM, and graphic image (Yantra), Swastika. He is known by other names such as Ganapathi (leader of the group), Vinayaka (remover of obstacles), Lambodara (pot-bellied one), Gajanana (elephant headed one) and Ekadanta (One-toothed).