or [Chibi](https://code.google.com/p/chibi-scheme). The later in that list you go, the more likely it
is that you'll have to compile the software yourself. (Thus Mac users will need Xcode.)
-Racket stands to Scheme in something like the relation Firefox stands to HTML. It's one program among others for working with the language; and many of those programs (or web browsers) permit different extensions, have small variations, and so on.
+Racket stands to Scheme in something like the relation Firefox stands to HTML. It's one program (or platform) among others for working with the Scheme language; and many of those programs (or web browsers) permit different extensions, have small variations, and so on.
Racket has several components. The two most visible components for us are a command-line interpreter named "racket" and a teaching-friendly editor/front-end named "DrRacket". You will probably be working primarily or wholly in the latter.
<!-- "racket" used to be mzscheme, "DrRacket" used to be DrScheme -->