All iDevice Operating System, e.g. iOS, updates are referred to as firmware updates.
So firmware is the layer between the application software and the device hardware. This is intended to enable applications to run without significant functional changes on multiple hardware versions. For example, updating iOS 14.4 to iOS 14.5 should not effect the User’s use of a particular app.
One can view this relationship as a four-layer stack where each layer depends on the layer supporting it:
- User
- Software (Application)
- Firmware
- Hardware (iDevice)