Broadly describe the significance of the grave digger's scene.

The grave digging scene in Shakespeare's Hamlet serves several dramatic purposes in the play.  First, it's about the only comic relief to be found in an otherwise unremittingly heavy, tragic play.  The two grave diggers tell a few jokes and their dialogue is full of puns and wordplay.  That's the most humor to be found in Hamlet.

The scene also serves to allow a philosophical reflection on life and death--right before most of the actual deaths in the play.  These observations serve as a foreshadowing and a contemplation on the brevity of life.  The skull of Yorick, the discussion of Alexander the Great, and the discovery that this is the grave of the young Ophelia all serve to remind Hamlet (and therefore us) that life is fleeting, and whatever is gained or achieved here on earth is quickly gone and buried and decomposed.  Death is the great equalizer.