Enotes responses are required to be a more substantial length than 25 words, so I'll just give you my characterization here, and then explain the reasons for it.
Hamlet is fundamentally about mortality; the imperfections in human thought, action and body. These corruptions make it impossible to achieve an ideal, the pursuit of which can lead to madness.
The link below, to the Enotes entry for themes in Hamlet, describes the importance of mortality, but also of revenge, insanity, moral confusion and national corruption. While it is sometimes said that King Hamlet's death catalyzes a series of "disturbances" in the universe of the play, representing the manner in which the fundamentally ordered and correct way of things is disturbed by this crime, this merely serves as a reason to exercise the themes and lessons that the play wishes to focus upon. For example, it is impossible for Hamlet to act in a morally responsible way, or in a way that fully restores justice, under the circumstances, and yet inaction is worst of all; Hamlet is obliged to damn himself one way or another. Under those conditions his inaction, and later madness, seem easily understood, as well as the inevitability of this outcome.
Shakespeare is the master of characterization. There is no one who can come closer to the genius of Shakespeare when it comes to creating marvellous and interesting characters. In Hamlet, his characterization is natural, spontaneous, vigorous and spirited. He depicts characters in such a way that we feel that the character is a living thing before our eyes. Characters come into life in his hands. Goethe says in this regard:
His characters are like watches with dial-plates of transparent crystal, they show you the hour like others, and the onward mechanism is also visible.
Shakespeare has used several tools of characterization to depict his characters in Hamlet. He uses Direct and Indirect Characterization to highlight essential traits of his characters. For example, what other characters say about the personality of Hamlet is an indirect characterization, while what we (audience) think about his personality is a direct characterization. The author has used dialogues, costumes and soliloquies to let us know about the character of Hamlet and other characters.