Baphomet 2.0
This drawing was taken from Eliphas Levi’s Dogme et Rituel de la Haute Magie (Dogma and Ritual of the High Magic). 
Baphomet, sometimes referred to as the Goat of Mendes, is, among other things, a potent symbol for the relationship between unity and duality. Light and dark, day and night, animal and human, male and female, creation and destruction. 
The Templars (and therefore the Freemasons) have been accused of worshipping Baphomet. There were attempts to tie the word etymologically to Mahomet (Muhammad), though it has been suggested that Baphomet may be a cipher for Sophia, referencing divine female wisdom. 
Aleister Crowley has added to the confusion. Read more if you want to see how he dragged the goat of Mendes into all of this. 
The Church of Satan adopted it in the 70s, ostensibly to freak out Jack Chick. Good work, Lavey. You scared an already-frightened old man.