Qt is a cross-platform application framework from Qt Software (owned by Nokia). It features a large number of libraries providing services like network abstraction and XML handling, along with a very rich GUI package, allowing C++ developers to write their applications once and run them unmodified in different systems. PySide aims to provide Python developers access to the Qt libraries in the most natural way.
PySide is built using the Shiboken binding generator.
The PySide class reference documentation is automatically generated from the original Qt documentation for C++, some parts were tuned to fit the Python world. However, it's not possible to rewrite all Qt docs as it would require a really huge effort, so if the documentation says you can use 0 on an QObject argument, interpret it as None.
Only optional arguments can be used as keyword arguments.
A collection of tutorials and "walkthrough" guides are provided with PySide to help new users get started with PySide development. These documents were ported from C++ to Python and cover a range of topics, from basic use of widgets to step-by-step tutorials that show how an application is put together.