Hamlet is a play about conflict, both external and internal. Externally, Claudius, Prince Hamlet's uncle, and Gertrude, his mother, have comitted horrific crimes. Claudius has murdered King Hamlet and Gertrude has betrayed her husband by marrying Claudius. Internally, Hamlet must struggle with wanting to avenge his father's murder, not feeling ready to assume the throne, and his own bravery to accomplish what needs to be done: exposing Claudius and his mother and letting the spirit of his father rest in peace. You can find much more information about Hamlet, the characters, and summary and analysis of the acts and scenes at the link below. Here is an excerpt from the eNotes introduction to Hamlet:
Shakespeare’s focus on this conflict was a revolutionary departure from contemporary revenge tragedies, which tended to graphically dramatize violent acts on stage, in that it emphasized the hero’s dilemma rather than the depiction of bloody deeds.