Well I believe only HubPages know the exact answer to this question but we can make assumptions. When you give a thumbs up to a hub then the rating of it goes up. This is almost surely automatic and the system sorts through the results and gives the hub an appropriate rating. When you thumbs a hub down then it will tell the team that this hub does not meet the minimum requirements for the website and if a hub receives multiple thumbs down, a worker will probably review it and may remove it based on the content.
As for the different categories of articles this probably determines which categories that the hub appears on the website. If it's "funny" then it may appear in the "Entertainment" section and so on.
Just reminding you that these are only assumptions on how the HubPages team sorts through the results of Hub Hopper.