RPython is the language used to create PyPy. Technically, it is considered a translation and support framework for implementing dynamic programming languages, separating the language specs from the implementation aspects. This means that RPython can be used for other languages besides Python, though it is most commonly associated with Python. This also means that any dynamic language will benefit from the JIT compiler and allows for a mix-and-match style when making implementation choices.
While certain environments have been created in the past to provide abstraction between source code and the target system, such as .NET and Java Virtual Machines, RPython uses a subset of CPython to create languages that act as simple interpreters, with little direct connectivity to low-level, system details. The subsequent toolchain creates a solid virtual machine for a designated platform by using the appropriate lower-level aspects as needed. This allows further customization of features...