PyUNO is a generic bridge between python and OpenOffice.org's component model UNO (Universal Network Objects).
The bridge enables python programmers to script a running OpenOffice.org -instance from the python executable via the UNO interprocess bridge. Additionally it allows to implement UNO components in python, which e.g. can be loaded directly into the OpenOffice.org process.
OpenOffice.org1.1rc ships with a nearly complete prebuilt python-2.2.2 runtime. This is necessary, because python 2.2.x does not yet build a shared library by default and the python executable is linked vs. the system's stdc++ library, which in general is incompatible to OpenOffice's stdc++ library.
In theory, PyUNO can also be used only with the core libraries of OpenOffice.org in order to use low-level-features like an interprocess bridge, C++ vs. Java vs. Python bridge, etc.
See http://udk.openoffice.org/python/python-bridge.html for a more detailed description of pyuno.