Windows 8 Refresh and Reset will both make it easier to clean malfunctioning systems and restore them to a working state, and Windows To Go offers new deployment features using Windows installations that run directly from USB.
Refresh preserves user settings, user data, and applications bought through the Windows store. Everything else is removed and restored to defaults. The process is quick, taking just a few minutes to complete.
Reset purges all applications and data, and reinstalls the operating system essentially from scratch. The OS is reverted to the same status as it would be after a clean installation. You have to re-enter a license key and perform initial setup once complete.
According to an arstechnica blog post;
Refresh and Reset both streamline a range of troubleshooting steps. Refresh handles situations where a system is behaving strangely for some reason—such as an application breaking a file association, or installing a load of unwanted startup programs—but which has valuable user data on it. Reset is for more serious problems, such as virus infection or some catastrophic system failure. It’s also ideal for preparing machines for resale.
Windows To Go is an enterprise-oriented feature that enables users to run Windows from USB thumb drives. Deployment to USB media uses the standard Windows imaging and deployment tools, such as ImageX and WIM images, and the result is a fully featured Windows install. The USB install is fully self-contained—it makes no changes to a system’s hard disk—and is fully updateable. New software can be installed, documents can be saved, Windows can be updated. It can be domain-joined and GPO-administered.