Wood is the captain of the Gryffindor Quiddich Team for the first 3 books in the series. Obsessed with Quiddich, he seems even more obsessed with winning - he will do anything to win and won't do anything after losing. All in all, he is unspeakably noble, ludicrously unintelligent, and as thick as his name implies. Oh well, you can't always win...
During his time at Hogwarts, Wood was the Gryffindor keeper, team manager, doctor, coach, etc. He designed ludicrously tough training programs and personally dragged his fellow team members out of bed to make sure they followed them. He also liked to think that he raised morale - his speciality was long, windy, pompously stirring speeches which the team were able to memorise by heart after several years of hearing the same thing (he spoke them so often).
He really is a minor character, but he is still quite funny. In the fourth book he has finished school and joins up on a professional team as reserve.