The sphinx was placed at the entrance to a temple to guard its mysteries for people entering the temple might steal the knowledge there. Knowledge was available for all but not given to all. People had to merit it, and to do so had to search for knowledge.
This mythical animal symbolised hidden knowledge. Interpreting the sphinx meant revealing what was hidden, thus acting as interpreter for the god Imen for he was the supreme representation of the world beyond our world (Imen means hidden). The Giza sphinx was not placed there to pose riddles, but rather to answer them.
This commemorative sculpture was placed at the foot of the pyramids to pay homage to the tawny, buff-coloured stone used to build them.
It was a hymn to the king of minerals, given that the sphinx had the body of a lion, king of the animals. But it had a human head meaning that Man was master of stone.
In the language of the Copts, a sphinx was called Bel-hit meaning guardian (of the horizon or of knowledge). During the Middle Empire it was called a Sheshep which meant secret representation (sech, writing and hep, secret). It often had an attributive adjective as in Sheshep-Ankh, thus being shown as living or as a concept that had come alive. It was also called Hor-em-Akhet (Harmakis in Greek) which can be translated by Hor on the horizon and therefore the light on the horizon.