Who is Sam from The Fall of Reach and what is their importance?

Sam (Samuel 034) is chosen to train as a Spartan. He is on John's original team when they first start training. Sam has sandy blonde hair and green eyes. He is also one of the Spartans John chooses for their first real life mission.

Sam recovers the fastest of the Spartans from the side effects of the augmentation process. He is also the strongest of the Spartans. When Sam is shot on one of their missions, John comes to the realization that the Covenant is not invincible.