[rules-users] Basic Questions

Hello, I've been reading about Jboss Drools and I have questions to do. 1. I still don't undertand why in the download section (about jboss rules) exist Jboss Rules and Drools. What's the difference? 2. When I downloaded the examples, I found files like .drl (drools files, they allow to write rules using a meta language), .dsl (I don't know how to use them) and .rule files. What's the difference? 3. How can I validate the rules from xml files? Thank you so much your help.