What are transaction applications (in Fiori)?

Transaction apps allow the end-users to perform transaction tasks such as creating purchase order requests. They represent simplified views and interaction with existing business processes and solutions. They run best on the SAP HANA database, but can also be used on top of other databases with acceptable performance. For the transactional apps, the ABAP front-end server contains the UI layer with the product-specific UI components for the products such as SAP ERP, CRM, SCM as well as the infrastructure components. The infrastructure comprises the central UI component with the SAP UI5 control library and the SAP Fiori launchpad as well as SAP Gateway with the OData enablement.