Amir's world is one of luxury and privilege. He is of the Pushtans (spelling??) and therefore he is among the majority as far as religion goes. He is also the sun of a very wealthy and influential man, which also allows him many of the privileges not given to the less wealthy (like school, for example). Amir recieves the best bike for his birthay, his father drives the nicest car and they live in one of the wealthiest and most beautiful neighborhoods.
Also, the world (the society) in which he lives is one where class and standing decide the entire fate of a human being; from birth one is designated as upper or lower class. This severly affects his relationship with his "friend" Hassan. Although the two grow up as brothers, Amir does not play with Hassan when other friends are around--they are of 2 different classes.
On the flipside, Assef, Amir's enemy, embodies all of the things that Amir's father wishes his son had (on the surface anyway). This complicates Amir's world further because he is constantly trying to live up to his father's expectations.