Hamlet and Laertes presumably grew up together, fencing with one another and confiding in one another. Then Hamlet went away to Wittenberg and Laertes to Paris, parting the friendship. Still, Hamlet refers to Laertes as "a very noble youth."
Hamlet recognizes what Shakespeare has made abundantly clear throughout the play, that Laertes is Hamlet's foil. He mirrors Hamlet but behaves in the opposite manner. Where Hamlet is verbal, Laertes is physical; where Hamlet broods, Laertes blusters. Laertes' love for Ophelia and duty to Polonius drive him to passionate action, while Hamlet's love for Gertrude and duty to King Hamlet drive him to passionate inaction. In Laertes resides the picture of what Hamlet could be if the sound of his own words did not mesmerize him.