There is a special security policy in Windows 10 that determines the behavior of Admin Approval Mode for the built-in administrator account. Users without administrative privileges have to additionally enter valid credentials for a local administrator account (UAC credential prompt). Members of the Administrators user group have to confirm or reject the UAC prompt without providing extra credentials (UAC consent prompt). The session will be temporary switched to the secure Desktop without open windows and icons, containing only an elevation prompt by the User Account Control (UAC). When its options are set to Always notify or Default, your Desktop will be dimmed. The UAC comes with different security levels. A good example would be the Registry Editor app. Usually, the apps that require elevation are related to the management of Windows or your computer in general. When some software tries to change system-related parts of the Registry or the file system, Windows 10 shows an UAC confirmation dialog, where the user should confirm if he really wants to make those changes. It tries to prevent malicious apps from doing potentially harmful things on your PC.
Since Windows Vista, Microsoft added a new security feature called User Account Control (UAC).
