Does my own created module depend on other modules like App Framework, UI Framwork or App UI?
Or is it possible to just create a web interface like described here: /chapter: Creating-Your-First-Module / OpenMRS Developers Guide (flossmanuals.net)
Whats the difference, or why would I need all the other modules mentioned above?
@armin its possible to make your module to depend on the UI framework see here Using the UI Framework in Your Module - Documentation - OpenMRS Wiki
but is it also necessary/mandatory or only kind of “nice to have”?
Using the UI Framework enables you to easily create a UI that fits in with the standard OpenMRS Reference Application look and feel and means that customisations you make to the reference application styles will be reflected on your pages.
Using the App Framework allows you to easily add buttons and links to existing parts of the OpenMRS Reference Application without needing to modify the source code for those pages.
There’s no strict requirement to use those features, but they’re intended to make your life easier and could make it easier to share your work with other developers and other implementors.