-Cython (http://www.cython.org) is based on Pyrex, but supports more
-cutting edge functionality and optimizations.
+Cython (http://cython.org) is a language that makes writing C extensions for
+the Python language as easy as Python itself. Cython is based on the
+well-known Pyrex, but supports more cutting edge functionality and
+optimizations.
+
+The Cython language is very close to the Python language, but Cython
+additionally supports calling C functions and declaring C types on variables
+and class attributes. This allows the compiler to generate very efficient C
+code from Cython code.
+
+This makes Cython the ideal language for wrapping external C libraries, and
+for fast C modules that speed up the execution of Python code.