I want to learn to program at least a little something for the Android. I've got Eclipse and the Android SDK's running OK on my PC, went through the "Hello, world" tutorial, it worked but I have no idea why.

Should I get a "Java/XML for Dummies" book to get me started on the very basics?

Would knowing Java and XML help me understand what all this is, or is Android a whole new language?

Understanding XML is not really necessary. But yes, you'd have to know Java for android developement. Reading one of those free android books would help, too