IronPython is an open-source implementation of the Python programming language which is tightly integrated with the .NET Framework. IronPython can use the .NET Framework and Python libraries, and other .NET languages can use Python code just as easily.

IronPython was first released in 2006, developed by a team led by Jim Hugunin, who is also the creator of Jython, a Python implementation for the Java platform.

The key features of IronPython include:

1. Seamless integration with the .NET ecosystem: You can import .NET namespaces and use .NET classes as if they were Python modules and classes.

2. Interoperability with other .NET languages: This means you can use IronPython scripts in a .NET application, use .NET objects in IronPython, or even inherit Python classes from .NET classes.

3. Hosting API: IronPython provides a hosting API for embedding the Python language into .NET applications.

4. DLR (Dynamic Language Runtime): IronPython was one of the first languages to leverage the DLR, which is a set of services added to the CLR (Common Language Runtime) for better support of dynamic languages.

5. Compatibility with Python: IronPython aims to be fully compatible with Python, although there may be some differences due to the underlying platform and the time lag behind the official Python releases.

However, as of my knowledge cutoff in September 2021, development of IronPython has slowed, and it may not be up-to-date with the latest versions of Python and .NET. Please check the latest information to get the most accurate status of IronPython.