Out of Browser (OOB)
Out of Browser (OOB) applications are executed out of the web browser, or that is the impression they give.
Regarding the final user, an OOB application is similar to a desktop application; the user installs it, gets a direct access icon to it, and when executed, it runs under a standard window, as shown in the following screenshot. It can even be uninstalled through the Control Panel.
From the point of view of the Software Developer, an OOB application still runs under a hidden browser, that is, it is a Silverlight application with the same features as an application running under a browser.
Until the arrival of Silverlight 5, the main difference with an application executing in the browser was the fact that it could work with trusted permissions and perform operations, which the sandbox normally does not allow (accessing the filesystem, executing commands via COM+, and so on).