Doc: update readme

Author: AlexyPellegrini

patch/SlicerCore/README.md

@@ -1,12 +1,58 @@
 # Slicer Core
 
-SlicerCore, formally known as "VTK MRML", is an alternative build-system for the 3DSlicer project.  
+SlicerCore is an alternative build-system for the 3DSlicer project.  
 It is intended to build a Python Package (wheel) from the core libraries and loadables modules of 3DSlicer.
 
+## About Slicer
+
+Slicer, or 3D Slicer, is a free, open source software package for visualization and image analysis.
+
+3D Slicer is natively designed to be available on multiple platforms, including Windows, Linux and macOS.
+
+For 3DSlicer community announcements and support, visit:
+
+    https://discourse.slicer.org
+
+For documentation, tutorials, and more information, please see:
+
+    https://www.slicer.org
+
+For 3DSlicer source code, please see:
+
+    https://github.com/Slicer/Slicer
+
+
+## About Slicer Core
+
+Slicer Core in a single sentence:
+***Slicer Core is the Python package consisting of all 3DSlicer modules that do not depend on Qt.***
+
+Slicer Core contains the following libraries of 3DSlicer:
+- `Base/Logic`
+- `Libs/*`
+- `Modules/Loadables/[MRML|MRMLDM|Logic|VTKWidgets]`
+
+This enables using 3DSlicer powerful MRML nodes system and associated medical-oriented algorithms in pure Python.
+
+## Using Slicer Core
+
+SlicerCore provides access to the main Slicer libraries through the slicer package namespace :
+
+```py
+from slicer import vtkMRMLScalarVolumeNode
+volume_node = vtkMRMLScalarVolumeNode()
+```
+
+Although the library can be used as is, additional convenience classes are provided in the trame-slicer Python package to initialize application logic and scene, wrap 2D and 3D views, provide applications on the web and more.
+
+For more examples, please visit the **[trame-slicer](https://github.com/KitwareMedical/trame-slicer)** project.
+
 ## Documentation and Examples
 
-- **[3DSlicer API documentation](https://apidocs.slicer.org/main/index.html)**
-- **[trame-slicer](https://github.com/KitwareMedical/trame-slicer)**: slicer-core usage example.
+- **[3DSlicer Developper Guide](https://slicer.readthedocs.io/en/latest/developer_guide/index.html)**
+    - Note that only some parts of the developper guide applies to Slicer Core as some modules and classes are not available.
+- **[3DSlicer API Documentation](https://apidocs.slicer.org/main/index.html)**
+- **[Trame Slicer](https://github.com/KitwareMedical/trame-slicer)**
 
 ## Acknowledgments