QGIS API Documentation  2.12.0-Lyon
Modules
Here is a list of all modules:
 QGIS core libraryContains all basic GIS functionality
 QGIS gui library.It's built on top of core library and adds reusable GUI widgets
 QGIS analysis library.Built on top of core library, the analysis library provides high level tools for carrying out spatial analysis on vector and raster data
 MapComposer
 QGIS network analysis library.The network analysis library provides high level tool for build topology and analysis it
 QGIS Server library.