This is a great question. This quotation comes from chapter nineteen of the book when Amir returns to Afghanistan to look for the son of Hasan to bring him back to the United States to atone for his "sins" of the past. In other words, Amir realizes that it is not too late to make things right and to stand up for what he believes in. So, with great courage, Amir returns to Afghanistan to look for the boy.
He meets Wahid and Farid. He comes to Wahid's home and the men drink tea together. After a while, Wahid's wife comes in to bring food. The food is set before Amir and she states that the family had already eaten. All the while he realizes that the boys were looking at his watch. So, he gives it to them. However, they are not interested in it so much. He, then, realizes that they were looking at his food. The boys were hungry.
This shows two things. First, it shows how much Afghanistan has changed with the arrival of the Taliban. The place is in shambles. Second, it shows that poverty of his old friends. Kabul is no longer the place it was before.