When you do a System Restore to a previous time, it does just that. It's like being a Time Lord, you can go back to yesterday.
From Help and Support:
System Restore helps you restore your computer's system files to an earlier point in time. It's a way to undo system changes to your computer without affecting your personal files, such as e?mail, documents, or photos.
Sometimes, the installation of a program or a driver can cause an unexpected change to your computer or cause Windows to behave unpredictably. Usually, uninstalling the program or driver corrects the problem. If uninstalling does not fix the problem, you can try restoring your computer's system to an earlier date when everything worked correctly.
System Restore uses a feature called System Protection to regularly create and save restore points on your computer. These restore points contain information about registry settings and other system information that Windows uses. You can also create restore points manually.
System Restore is not intended for backing up personal files, so it cannot help you recover a personal file that has been deleted or damaged. You should regularly back up your personal files and important data using a backup program.