There are several parts to Lux's rendering API:
This library handles ray intersection on OpenCL devices. More information can be found on the wiki: LuxRays overview
This library is the full LuxRender system. Its API is C-style and exposed via api.h.
This is an OO python wrapper around the C API, providing access to LuxRender via the python programming language.
PyLux is documented here: PyLux Documentation.