Here is a list of all documented namespaces with brief descriptions:
[detail level 123]
  NXOpen | Provides classes and interfaces for the NX Open Common API |
  Annotations | Provides classes and interfaces relating to Dimensions, Notes, Symbols, PMI, and other Annotations |
 Assemblies | Provides classes and interfaces for Assemblies |
  ProductInterface | Provides classes and interfaces for Assembly Product Interfaces |
| BlockStyler | Provides classes and interfaces for the Block Styler |
| BodyDes | Provides classes and interfaces for Body Design |
| CAE | Provides classes and interfaces relating to Advanced Simulation and Design Simulation |
| Connections | Provides classes and interfaces relating to Connections |
| FTK | Provides classes and interfaces to Function Toolkit |
| ModelCheck | Provides classes and interfaces relating to Model Check |
| Optimization | Provides classes and interfaces relating to Optimization |
| ResponseSimulation | Provides classes and interfaces for Response Simulation |
| Xyplot | Provides classes and interfaces for XY Graphing |
| Cam | Provides classes and interfaces for Manufacturing |
| CAM | Provides classes and interfaces for Manufacturing |
| FBM | Provides classes and interfaces to Features Based Modeling |
| Die | Provides classes and interfaces relating to Die Engineering and Die Design |
| Display | Provides classes and interfaces for Display |
| Drafting | Provides classes and interfaces for the Drafting |
| Drawings | Provides classes and interfaces for Drafting Drawings |
| Facet | Provides classes and interfaces for Faceted Representations |
| Features | Provides classes and interfaces for features |
| SheetMetal | Provides classes and interfaces for Sheet Metal Features |
| ShipDesign | Provides classes and interfaces for Ship Design |
| Subdivision | Provides classes and interfaces for Subdivision Body feature |
| VehicleDesign | Provides classes and interfaces for Vehicle Design |
| Fields | Provides classes and interfaces for Fields |
| Formboard | Provides interfaces and classes to the Routing Electrical Formboard functionality |
| Gateway | Provides classes and interfaces for Gateway |
| GeometricAnalysis | Provides classes and interfaces for Geometric Analysis |
| SectionAnalysis | Provides classes and interfaces for Section Analysis |
| GeometricUtilities | Provides classes and interfaces for Geometric Utilities |
| Issue | Provides classes and interfaces for Issue Management |
| Layer | Provides classes and interfaces for layer |
| Layout2d | Provides classes and interfaces for Layout2D |
| LineDesigner | Provides classes and interfaces for Line Designer |
| Markup | Provides classes and interfaces relating to Markup |
| MechanicalRouting | Provides classes and interfaces for MechanicalRouting |
| Mechatronics | Provides classes and interfaces for Mechatronics |
| MenuBar | Provides classes and interfaces for the Menu Bar |
| ModlDirect | Provides classes and interfaces for Direct Modeling |
| Motion | Provides classes and interfaces for Motion Simulation |
| OpenXml | Provides classes and interfaces for Open XML |
| Optimization | Provides classes and interfaces for Optimization |
| Options | Provides classes and interfaces for options |
| PartFamily | Provides classes and interfaces for Part Family |
| PDM | Provides classes and interfaces for PDM |
| PhysMat | Provides classes and interfaces for Physical Material |
| Placement | Provides classes and interfaces for Placement |
| Positioning | Provides classes and interfaces for Assembly Positioning and Constraints |
| Preferences | Provides classes and interfaces for preferences |
| Report | Provides classes and interfaces relating to Report |
| Routing | Provides classes and interfaces for Routing |
| Electrical | Provides classes and interfaces for Routing Electrical |
| ShapeSearch | Provides classes and interfaces for Shape Search |
| SheetMetal | Provides classes and interfaces for Sheet Metal |
| ShipDesign | Provides classes and interfaces for Ship Design |
| SIM | Provides classes and interfaces for Machine Tool Builder and CAM-Simulation |
| PostConfigurator | Provides classes and interfaces for Post Configurator |
| Tooling | Provides classes and interfaces for Tooling |
| UIStyler | Provides classes and interfaces for User Interface Styler |
| UserDefinedObjects | Provides classes and interfaces for User Defined Objects (UDOs) |
| UserDefinedTemplate | Provides classes and interfaces for User Defined Template |
| Validate | Provides classes and interfaces for Validation Utilities |
| VisualReporting | Provides classes and interfaces for Visual Reporting |
| Weld | Provides classes and interfaces for Weld |