Update README.md

src/modules/README.md

@@ -2,4 +2,14 @@ Calamares modules directory
 ===
 
 Calamares modules are plugins that implement the Calamares module API and can provide features like installer pages, batch jobs, etc.
-To add a module, put it in a subdirectory and make sure it has a CMakeLists.txt, it should be picked up automatically by our CMake magic.
+
+### Qt plugin viewmodules
+
+Currently the only way to write a module which exposes one or more installer pages (viewmodule) is through a Qt plugin. Viewmodules should implement `Calamares::ViewStep`. They can also implement `Calamares::Job` to provide jobs.
+
+To add a Qt plugin module, put it in a subdirectory and make sure it has a `module.conf` and a CMakeLists.txt with a `calamares_add_plugin` call. It will be picked up automatically by our CMake magic.
+
+
+### Python and process jobmodules
+
+Batch jobs for Calamares can be written as Python scripts or as generic commands (shell scripts, external programs, etc.). To add a Python or process jobmodule, put it in a subdirectory and make sure it has a `module.conf`. It will be picked up automatically by our CMake magic. CMakeLists.txt is not used for Python and process jobmodules.