From the article : what is a WebOS (not to be confused with another definition of the term, see here), or a Webtop, anyway ? Here’s a simple definition: WebOS is a virtual operating system that runs in your web browser. More precisely, it’s a set of applications running in a web browser that together mimic, replace or largely supplement a desktop OS environment. It’s a tough field to start in for a Web 2.0 entrepreneur, because to be successful you need to create several applications that are at least as good as other competitors, and you need to connect them all into a usable bundle. What’s also expected by most users is that all this looks decent, operates similarly to a “real” OS and behaves as a real “OS” would, and is relatively bug-free. Simply put, to gain real everyday users, your WebOS has to be damn good. We’ll see how these newcomers fare in the following months and when (and if) some big giant like Google decides to create their own WebOS.