Making sense of jQuery/Prototype debates

Making sense of jQuery/Prototype debates

So for a research topic at school, I chose to do web development software trends, to see if there are any general commonalities.  One sub-topic I chose to do was Javascript, and where it seems to be heading.  After reading a bit about it (I'm very new to web development), I learned that jQuery and Prototype seemed to be the most popular options when using javascript, but I didn't understand why they are compared against each other so often.  If jQuery is a library, and Prototype is a framework, why would people only choose one or the other?  I know some people use both, and I also realize that there's minor conflicting syntax issues, but I was hoping someone with more experience could help me understand why a framework and a library can be compared head to head.

thanks,
Phil