Ganesha also spelled Ganesa and Ganesh, and known by names as Ganapti, Pillaiyar, or Vinayaka is one of the most well know and worshipped deities in Hinduism as well as many other Eastern Religions. While Ganesha is known by many attributes he is most commonly associated with his large elephant head and multiple arms. Ganesha is widely revered as the Remover of Obstacles and the deva of intellect and wisdom. While often considered the remover of obstacles both materially and spiritually, traditionally he can also place obstacles in the way of people who need to be checked. Ganesha is the son of Shiva and Parvati.
The earliest known occurrences of the deity being used in popular culture date back to at least the 4th century during the Gupta Period, the Gupta Dynasty ruled much of India from 280 to 550 CE. Throughout history Ganesha has shown a wide variety of patterns and portrayals unlike many of the deities that are very strict and have minimal representations as far as pose, size, etc. Indian art shows great variation from standing, dancing, taking action against demons, and even playing with his family as a boy.
However he may be depicted by whatever religion that worships him, he has become an icon of material and spiritual obstacles. For further information on the history and religions that worship him please see the wiki article.