This scene in Act 5, sc. 1, shows a great deal about the character of Hamlet.  He sees the gravediggers going about the business of digging a grave and making jokes about it. Horatio has to remind him that the gravediggers have become hardened about their jobs and that's why they make jokes.  That Hamlet questions their frivolous nature at such a task shows the audience he is a sensitive man.  Then as the gravediggers unearth old skulls, Hamlet ponders who they might have been and if they were pompous and thought highly of themselves during their lifetimes.  When the first gravedigger identifies one of the skulls as that of Yorick, the jester with whom Hamlet played as a child, Hamlet becomes very thoughtful and ponders about life and death.  He says that no matter how high a person might be in life, in death, all are equal.  Death is the great neutralizer making the king no greater than the pauper.  This isn't the first time Hamlet has pondered life, its meaning, and death.  Most of his soliloquies get into those subjects at least somewhat, especially the "To be or not to be" soliloquy of Act 3, sc. 1.  But this pondering at the sight of what is to be Ophelia's grave, shows the audience again what a deep thinker Hamlet is.  Even in the midst of much personal turmoil, he is a man who thinks about man's existence and its meaning.  Death is the main topic of "Hamlet" from the beginning mention of visits by the ghost of King Hamlet to the end and the deaths of four major characters including Hamlet.  Hamlet's ponderings in the graveyard scene show the audience that Hamlet isn't terribly afraid of death despite what he said in Act 3, sc. 1.  He is more curious than afraid.