SaaS means Software as a Service, and is the provision of complete cloud software applications over the internet.
Examples of SaaS application are Office 365 and Dynamics 365.
You typically pay for SaaS applications on a per user per month/year.
The shared responsibility model applies, it is just that the cloud provider takes more of the responsibility in making sure the systems are up to date and available.
More information
https://azure.microsoft.com/overview/what-is-saas/
This post is part of a series for preparing and revising for the Dynamics 365 Fundamentals exam, MB-900. You can find the whole series here.
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