A contract between the cloud provider and the customer that specifies the guaranteed availability level for a service, and the compensation (service credits) if it is not met.
In AZ-900: Azure SLAs range from 99.9% to 99.99% depending on the service and configuration (e.g. VMs in an availability zone get a higher SLA). CLF-C02 applies the same logic. Frequent question: which configuration raises the composite SLA.
SLA (Service Level Agreement) is a concept that can show up on the exam. Check the full guide to see it in context.