Application Sandboxing is a feature of ACS that limits the environments in which certain code can execute. In other words, it means running a process in a Job that limits its ability to interact with other processes, as well as some specific types of interactions with the operating system, such as:
- Reading or writing from the clipboard
- Shutting down the system
- Adjusting display settings
To a large extent in the post-Windows Vista era, most of the benefits of cross-process protection are mitigated by the Integrity Level (IL) mechanisms introduced.
Some of the internet facing apps today (such as IE, Chrome, Word, Adobe Reader) already implement their own extended sandboxing. As such, this mechanism would not apply to them.
Further reading that Application Sandboxing in Windows can be found at:
http://www.chromium.org/developers/design-documents/sandbox
http://www.chromium.org/developers/design-documents/sandbox/Sandbox-FAQ