The tour takes place in a Unix environment. CVS also runs on Windows and Macintosh operating systems, and Tim Endres of Ice Engineering has even written a Java client (see http://www.trustice.com/java/jcvs/), which can be run anywhere Java runs. However, I'm going to take a wild guess and assume that the majority of CVS users – present and potential – are most likely working in a Unix command-line environment. If you aren't one of these, the examples in the tour should be easy to translate to other interfaces. Once you understand the concepts, you can sit down at any CVS front end and work with it (trust me, I've done it many times).
The examples in the tour are oriented toward people who will be using CVS to keep track of programming projects. However, CVS operations are applicable to all text documents, not just source code.
The tour also assumes that you already have CVS installed (it's present by default on many of the popular free Unix systems, so you might already have it without knowing it) and that you have access to a repository. Even if you are not set up, you can still benefit from reading the tour. In Repository Administration, you'll learn how to install CVS and set up repositories.
Assuming CVS is installed, you should take a moment to find the online CVS manual. Known familiarly as the "Cederqvist" (after Per Cederqvist, its original author), it comes with the CVS source distribution and is usually the most up-to-date reference available. It's written in Texinfo format and should be available on Unix systems in the "Info" documentation hierarchy. You can read it either with the command line info program
floss$ info cvs
or by pressing Ctrl+H and then typing "i" inside Emacs. If neither of these works for you, consult your local Unix guru (or see Repository Administration regarding installation issues). You'll definitely want to have the Cederqvist at your fingertips if you're going to be using CVS regularly.