What does a component "know"?

Denise Bowker

When a component's XSL is being processed, what does it know about its environment? For example can it find out:
1) the "site"
2) the "url"
3) the Page Layout section (header, body, footer, ...)
4) ...

(and if so, how do I get it?)

As I continue on this I also need to know what environment I'm in (development, testing, production) since my external resources have different URLs depending upon which environment.

I would like to build a component that will be used on multiple sites, but it looks totally different based upon the site it's on. I would rather not have separate components, it would be nice if the people who build the pages can always use the same component regardless of where it's going to live.