Kyon is the narrator and the main protagonist of the series. He is a student, with whom Haruhi willingly interacted. Even though Haruhi is the title character, the story is told through his viewpoint. Through narration and dialogue, he provides his insight, perspective, and opinions on the series' events.
While Kyon's intentions toward defending his Brigade fellows from Haruhi's madness are often well intentioned, he often has to struggle to overcome the crazy and often ridiculous obstacles barring his way. While he's not afraid to stand up to a Haruhi tangent, he does exhibit a form of fear over her occasional troublesome antics that could threaten expulsion or worse.

Kyon is, in fact, a nickname. Kyon's real name has yet to be revealed.

Source:Wikipedia