Simple definition
A vSAN storage policy specifies availability, placement, and performance requirements for virtual machine objects.
Purpose and use
A vSAN storage policy expresses protection and service requirements for VM objects.
How does it work?
The platform translates them into placement and protection according to capabilities, topology and available resources.
Example and verification
Check actual object compliance and cluster health after a failure or configuration change.
Points to watch
Assigning a policy does not guarantee compliance. Fault domains and available capacity determine what is achievable.
In short
Verify the declared requirement separately from its effective compliance.