"Portable Python" is a distribution of the Python programming language that
- can be run without installing it.
- from a USB drive, for example.
- includes many extras such as different IDEs, wxPython, etc.
- the exact set of extras available depends on the version of Python.
- can be obtained for Python 2.5, 2.6, or Python 3.0.
- is only available for Windows.
If it interests you, another analagous distribution is MovablePython.