In this scene Hamlet is contemplating suicide because of all the events that are happening in his life. Hamlet decides that he will never to go through with killing himself because fear holds us back.
In this scene Ophelia is ending things with hamlet for good. Because Hamlet was just dealing with his friends lying to him, he ends up getting angry with her and getting generally mad at all women.
In this last scene Hamlet is trying to see if his plan to catch the king in in his guilt ends up working. During the performance the king demands the play be stopped and hamlet is now ready avenge his father.