Maha Ganesh represents the energy of Lord Siva and Goddess Parvathi (Uma). Because of a mythological incident, the normal head of Ganesha had to be replaced with that of an elephant. The elephant-headed Ganesha looks like OM, the pranava mantra, representing the quintessence of the Vedas (Hindu scriptures), indicating power and wisdom.
Eka dhantham Maha kayam, Lambo dara Gajananam
Vigna nasa karam devam, Herambam Pranamam yaham
I salute the Lord Heramba (the self-effulgent Ganesha), the one who destroys all obstacles, who has a huge body, a face that of an elephant and only one tusk.