The Az-900 exam tests your foundational knowledge of cloud concepts and Microsoft Azure services. It validates your understanding of core Azure concepts, including security, privacy, compliance, and trust. One of the key objectives of the exam is to assess your understanding of cloud computing principles. This includes knowing the different types of clouds (public, private, hybrid) as well as various cloud deployment models (IaaS, PaaS, SaaS). You should also be familiar with virtualization technologies and their role in cloud computing.