If you want to understand what context-driven testing is all about, James Bach and Cem Kaner have recently collaborated on a statement of what it is, and a lengthy explication. It’s posted on Cem Kaner’s blog at http://www.satisfice.com/kaner. The posting covers the territory admirably, and I wholeheartedly agree with it.
In particular, the statement emphasizes that adaptation to the needs of the project is the first step in the context-driven approach. This makes context-driven distinct from other approaches that may acknowledge the importance of context, but make something else—a standards focus, iterative development and unit tests, “best practices”, a particular process model—paramount.