A model where the provider manages everything: infrastructure, platform, and application. The customer simply uses the software through a browser or client app. This gives the user the lowest level of control.
In AZ-900: Microsoft 365, Dynamics 365. In CLF-C02: Salesforce, Gmail. A typical question: with SaaS the customer manages nothing except their data and basic user configuration — the provider is responsible for everything else.
SaaS (Software as a Service) is a concept that can show up on the exam. Check the full guide to see it in context.