Add text defining terms "Pyodide" and "Emscripten Python"

Author: hoodmane

peps/pep-0776.rst

@@ -72,6 +72,37 @@ Packaging Goals
 Emscripten Platform Information
 ===============================
 
+"Pyodide" vs "Emscripten Python"
+--------------------------------
+
+For the sake of this document, we use the term "Emscripten Python" to refer to
+the Emscripten Python maintained in the ``python/cpython`` repository, without
+any downstream additions. We contrast the features present in Emscripten Python
+to the features present in Pyodide.
+
+Pyodide is maintained `on github <https://github.com/pyodide/pyodide>`__ and
+distributed via `jsDelivr <https://www.jsdelivr.com/oss-cdn/pyodide>`__, `npm
+<https://www.npmjs.com/package/pyodide>`__, and `github releases
+<https://github.com/pyodide/pyodide/releases>`__.
+
+Emscripten Python is not distributed, but it is possible to build and test by
+executing the following commands from the root of the CPython repository:
+
+.. code-block:: sh
+
+    # Install Emscripten
+    git clone emscripten/emsdk
+    ./emsdk/emsdk install 4.0.5
+    ./emsdk/emsdk activate 4.0.5
+    source ./emsdk/emsdk_env.sh
+
+    # Build
+    python3.12 ./Tools/wasm/emscripten/ build
+
+    # Run the test suite
+    ./cross-build/wasm32-emscripten/build/python/python.sh -m test
+
+
 Background on Emscripten
 ------------------------