What exactly is the rheumatoid factor?

I was told over a year ago that on top of OA, I had an extremely high RF. When I finally saw a Rheumatologist she said that while the number was very high, my joints were still "juicy".

I really have no idea what any of that means. I do know that my hands spaz out and lock up up painfully sometimes several times a day. But I can also go days or weeks without an episode.

I would very much appreciate having some things explained to me. I haven't had the best experiences with doctors lately and have developed a general lack of faith in their concern over my welfare. Everyone seems to be more concerned with my insurance than my well being.