Device compliance is a way to decide whether a computer or mobile device meets company security requirements.
A compliant device might be required to have encryption enabled, a supported operating system, active security software, and a screen lock.
Intune can evaluate the device and report whether it meets the rules.
Conditional Access can then use that information. For example, a company may allow Microsoft 365 access only from devices that meet its security standards.
Compliance policies are useful because they turn company expectations into measurable requirements.
The rules should be realistic and tested. If they are too strict, employees may be blocked from normal work.
The goal is to make sure devices handling business information meet a reasonable level of protection before they are trusted.