Simple definition
An Intune security baseline provides a recommended set of device security settings that administrators can customize.
Purpose and use
An Intune security baseline supplies a versioned set of recommended protection settings for compatible products.
How does it work?
An organization creates a profile from this starting point and can adjust values; baseline versions can introduce changes.
Example and verification
Before deployment or upgrade, compare settings and test their effect on a pilot group's applications and workflows.
Points to watch
A baseline is not a security certification and does not automatically resolve conflicts with other profiles or Group Policy.
In short
It provides a starting configuration that needs contextual justification, monitoring and verification.