Explanation
The Master Policy is a set of rules that apply to all accounts in the Vault. However, one can create exceptions to the Master Policy based on platforms, which are logical groupings of accounts that share common characteristics, such as operating system, device type, or application. By creating platform-specific policies, one can override the Master Policy settings for certain accounts and customize the security and management options for different platforms. References:
* Defender PAM Sample Items Study Guide, page 9
* CyberArk Core Privileged Access Security Documentation, Master Policy Overview and Platform-Specific Policies