ReCaptcha

I don't understand this whole ReCaptcha thing. You know, like the sample here (Don't bother trying it, it's just a picture). Now I'm all for stopping spam and for reading books, too. That's not the problem. What I don't get is:

• If I am helping the computer to read, How does it know when I am right? If it already knows what these words are then why am I telling it? It doesn't seem helpful. I should be helping it to read words that it couldn't read for itself. But that brings us back to the first question.
• What kind of book am I reading? I can't even figure out if it is fiction or non fiction. I can't get a sense of plot and there is no continuity of characters. Who is this Oeser anyway? Is it a guy or a girl. What does the organization have to do with it? Maybe it's something to do with business. I don't know. There's no connection between these words and the last two I saw, either.