Hi,
It depends on the type of deployment.
In cloud deployment, database is SQL Azure and on Premises uses SQL Server 2016 standard or enterprise edition. Client represents client components such as web browser client, mobile apps(IOS, Android, Windows) and office 365 (for both deployments).
In cloud deployment, AOS would be AOS web App on IIS and batch windows service and on premises its Service fabric standalone cluster(with minimum 3 nodes recommended for AOS/Batch/Data management).