it points out that death is the great equalizer and has no respect for earthly ideals of rank or caste (to death a bum and the king are the same and the same goes for the wise man and the fool --just another "body") --- basically it means --you can't take it with you --not honors nor glory nor wealth --- so do good with the items you have control over while you live --- power / titles / honor / weaith do mean something to the living --- however they mean nothing in the grave.
in other words by just looking at these 4 sets of bones --can you tell which set of bones were the kings / the beggers-/ the wise mans / the fools --- well which was which ? thus a lesson is learned . in death all are equal.
the triangle has 3 sides ---- --birth --life--death -- the holy trinity --(father/ son / holy spirit )=== creator --existance--death
the sphinx -- the great "puzzle" oif life to be solved
