What is UI5?
The UI5 framework provides concepts such as components (referred to in other frameworks as applications and/or reuse composite components), Model-View-Controller pattern to structure the application, routing to manage navigation between views, integrated data binding and more.
In UI5, so-called controls (respectively UI elements; in Simplifier they are called Widgets) are used to assemble the user interface. A major benefit of UI5 is that they come with a wide variety of bread & butter, layout, and complex controls to build your application.
Learn more about the difference between OpenUI5 and SAPUI5 here.
What is SAP Fiori?
The SAP Fiori design philosophy is based on five core principles. The SAP Fiori user experience is role-based, adaptive, simple, coherent, and delightful.
The UI5 framework is aligned with the SAP Fiori design guidelines so that Web applications created with UI5 deliver a consistent user experience.
Is UI5 self-contained or does it use open source?
UI5 uses open-source software. There are a number of open-source libraries that are included in the UI5 framework. The best-known example of using open-source is jQuery.
What is a UI5 control?
UI5 controls are the built-in offering of the UI5 framework for writing UI elements. A special feature is the out-of-the-box data binding support, which allows the controls to be easily bound to data from different models.
Take a look at this blog post to learn more about UI5 Framework and UI5 Web Components.