File permissions in Windows determine who can access, modify, or execute files and folders on a drive. Managed through Access Control Lists (ACLs), permissions assign specific rights (like Read, Write, Modify, Full Control) to individual users or groups. This differs from simply marking a file as "read-only," which applies globally without distinguishing between users. It provides granular control over security.

Practically, you can change permissions using File Explorer: right-click a file/folder, select "Properties," go to the "Security" tab, select a user/group, click "Edit," and assign/deny specific permissions. System administrators often use PowerShell commands (Set-Acl, icacls) for scripting bulk permission changes across network drives or server directories. For example, an IT team might restrict Write access to a shared "Projects" folder for contractor accounts.

While essential for security, managing Windows file permissions can be complex for non-technical users, particularly troubleshooting access denied errors or inheritance issues. Proper permission setup prevents unauthorized data access or modification, forming a key part of ethical data handling. Future developments increasingly integrate cloud identity management, potentially simplifying on-premises permission workflows while shifting security models to cloud platforms.