Rosencrantz and Guildenstern are in Denmark, ostensibly to see Hamlet on a random visit, but in reality because they were summoned by Claudius to see if he could use them to get some better idea of what is up with Hamlet.
As they meet Hamlet, he questions them on why they are there, on whether they were sent for and also comments on his present situation giving the audience some insight. He feels that Denmark is a prison, in fact the whole world is a prison because he is bound by his "bad dreams" and by his inability to reason. He also feels he is "dreadfully attended" by people who all want to know what is wrong but won't accept the real answer.
He has "lost all [his] mirth" and so lost all his delight in companionship, etc., for he is concerned only with the weakness of his own humanity and inability to act.
As was mentioned in the previous post, Rosencrantz and Guildenstern are in Denmark to visit their friend, Hamlet. Claudius then summons the two friends to try to find out what is bothering Hamlet. In Act Two, Scene 2, Hamlet is excited to see Rosencrantz and Guildenstern. Hamlet asks his friends why they decided to visit Denmark. Hamlet goes on to say that Denmark is his personal prison, and his two friends disagree with his evaluation. Hamlet proceeds to tell his friends that he has been having terrible dreams. After Rosencrantz and Guildenstern admit that the king and queen have sent them, Hamlet discloses his anxiety and depression. He mentions that the whole world feels sterile and empty to him. Hamlet's comments provide the audience with insight into his character. Hamlet is utterly consumed with his decision to avenge the murder of his father. Hamlet's despair consumes him and has also negatively affected his health. Throughout this interaction, the audience realizes the extent of Hamlet's depression and gains insight into the consequences of his indecision. With the exception of Horatio, Hamlet no longer trusts anyone and feels even more isolated knowing that Claudius and Gertrude have influenced Rosencrantz and Guildenstern.