When Amory first gets to Princeton, he doesn't have anyone to talk about deep philosophical ideas with. Until he meets Tom, that is. Amory actually knows Tom by reputation before he meets the guy. Tom is something of a fancy-pants poet. You know, the kind of guy who rocks a beret, black turtleneck, and French cigarette.
When Amory finally meets him, he sees that Tom:
…was, perhaps, nineteen, with stooped shoulders, pale blue eyes, and, as Amory could tell from his general appearance, without much conception of social competition and such phenomena of absorbing interest. (1.2.136)
In other words, Tom is a guy who thinks about big, beautiful ideas without any real regard for the everyday world and its petty, competitive views. Who can blame him? The world that Amory inhabits seems pretty nasty, and we can only imagine it's nicer to keep your head in the clouds.
Deep down, Amory can't really handle the idea that someone could be so free from the world of superficial, judgypants people. In fact, he works hard to make Tom notice this world more often. As the narrator tells us, "In the meanwhile Amory delicately kept trying to awaken a sense of the social system in D'Invilliers, for he knew that this poet was really more conventional than he" (1.2.153).
Basically, Amory is shaking poor Tom and screaming "Wakey wakey, eggs and bakey! The world sucks." Amory's relationship with Tom is sort of love/hate. On the one hand, he admires Tom's ignorance of social conformity. On the other hand, he wants Tom to be more normal because he (Amory) is jealous of him.