The Open Education Consortium has declared this "The Year of Open" (sounds like a good theme for any year!). To celebrate, they're publishing long answers to straightforward questions on complex topics. I've contributed my own response to "What is the Open Web?" and it's now available:
The "open Web" is the idea that the World Wide Web should remain accessible to as many people as possible. It has both technical and cultural dimensions.
Technically speaking, the open Web is a series of technological standards and protocols that govern certain modes of interaction between humans and computers. We might think of "protocols" as sets of rules that define what's acceptable and expected (indeed, what's possible) when two or more of these agents attempt to interact.
Culturally speaking, the open Web is something more akin to a spirit or ethos—a belief that adhering to standards is not only welcome or desirable but fundamental to the continued operation and utility of the World Wide Web itself. It's a set of principles and practices that its advocates advance as the "right way" to organize, maintain, control, and grow the World Wide Web. This facet of the "open Web" concept usually manifests in discussions about Web etiquette and "best practices."