This is a high-level diagram that shows all the major components of the subject application, including related databases and any other systems to be integrated. It includes the messaging, protocols, and services that are available as well as the connections from the external endpoints to the application's user interface and APIs.
It also includes the logical breakdown between what is hosted on the application server tier and what is hosted on the database server tier.
This is a block diagram showing the tiers, layers, and standards used by the subject application, including related databases, to provide (typically) data access, business logic, services, user-interface, administration, security, and inter-process-communications within its stack. The diagram identifies the platforms, frameworks and libraries that are being used:
We have attached a powerpoint presentation version of these two diagrams as well.