What defines the rules and settings that devices must comply with in Intune?

The correct choice is compliance policy, as it specifically outlines the requirements and rules that devices must adhere to in order to be considered compliant within Microsoft Intune. Compliance policies are critical for ensuring that devices meet the organization's security and operational standards. This includes aspects like requiring encryption, specific operating system versions, password policies, and whether the device is managed or monitored.

By establishing these rules, compliance policies enable the organization to enforce security measures and can trigger actions based on compliance status, such as removing access to company resources if a device does not meet the necessary standards.

Other concepts, while important in the management of devices in Intune, serve different purposes. Security baselines provide a set of pre-configured security settings that can be applied to devices, device configuration policies determine the specific settings to apply to devices (like Wi-Fi, VPN, etc.), and app protection policies focus on securing applications and managing how corporate data is accessed and used on both managed and unmanaged devices. Each of these has its role, but none are focused solely on ensuring device compliance like the compliance policy does.