The topic of the passage is a duel between Laertes and Hamlet.
The King Claudius has bet that Hamlet can beat Laertes in a duel. Hamlet has killed Polonius unintenionally, so Laertes is wiling to fight with him in order to avenge the death of his father. Meanwhile, it is a good opportunity for Claudius to eliminate Hamlet, who suspects he has murdered his father to become king and marry his mother.