IronPython follows the specification of the Python language as found on the main Python web site http://docs.python.org
There are minimal differences. The most significant difference is the IronPython treats all strings as unicode (in that respect it is very similar to Python3). For a complete list, see http://ironpython.codeplex.com/wikipage?title=Differences

Developer documentation for IronPython (and IronRuby) can be found at https://github.com/IronLanguages/main/wiki

There is a good source of general IronPython documentation at http://ironpython.net/documentation

There is also an IronPython cookbook with numerous code samples at http://www.ironpython.info