# What is PyPy?

Historically, PyPy has been used to mean two things. The first is the RPython translation toolchain for generating interpreters for dynamic programming languages. And the second is one particular implementation of Python produced with it. Because RPython uses the same syntax as Python, this generated version became known as Python interpreter written in Python. It is designed to be flexible and easy to experiment with.

To make it more clear, we start with source code written in RPython, apply the RPython translation toolchain, and end up with PyPy as a binary executable. This executable is the Python interpreter.

Double usage has proven to be confusing, so we've moved away from using the word PyPy to mean both toolchain and generated interpreter. Now we use word PyPy to refer to the Python implementation, and explicitly mention RPython translation toolchain when we mean the framework.

Some older documents, presentations, papers and videos will still have the old usage. You are hereby warned.

We target a large variety of platforms, small and large, by providing a compiler toolsuite that can produce custom Python versions. Platform, memory and threading models, as well as the JIT compiler itself, are aspects of the translation process - as opposed to encoding low level details into the language implementation itself.

For more details, have a look at our architecture overview.