On the Frequently Asked Questions page Google makes it very clear that "Because web apps listed in the Chrome Web Store are regular web applications, built with standard web tools, they can be used by anyone using a modern browser that supports these web technologies. Users accessing the Chrome Web Store through Google Chrome will have the ability to create convenient shortcuts for easily accessing their apps."
Continuing, the page notes, "When Google Chrome users "install" a web application from the store, a convenient shortcut is added for quickly accessing the app. Installed web apps can also request advanced HTML5 permissions. For more information, read the preliminary documentation about installable web applications in Chrome."
According to Erik Kay, Lead Software Engineer on the project, "We believe it should be easier for users to discover web apps and for developers to reach a large audience. That's why today at Google I/O, we announced the Chrome Web Store, an open marketplace for web apps.
Google Chrome users who find web apps in the store will be able to create convenient shortcuts in Chrome for easy access. Also, developers will have the option to easily sell their apps through the store using a convenient and secure payment system.
According to the Google Code Labs page "An installable web app is a normal web site with a bit of extra metadata. You build and deploy this app exactly as you would build and deploy any web app, using any server-side or client-side technologies you like. The only thing that is different about an installable web app is how the app is packaged."
This is a very interesting development in the area of mobile applications. Clearly it will destroy a little of the "secret sauce" of other platform-specific App Stores. One wonders what moves such vendors will make to increase the 'difficulty' of using such applications on their platforms.