Update DESIGN.md

docs/DESIGN.md

@@ -28,8 +28,11 @@ An app is simply a `git` repository with some additional files on the top level,
 So a Python application could have a `Procfile` like such:
 
 ```bash
+# A module to be loaded by uwsgi to serve HTTP requests
 wsgi: module.submodule:app
-worker: python long_running_script.py 
+# A background worker
+worker: python long_running_script.py
+# Another worker with a different name
 fetcher: python fetcher.py
 # Simple cron expression: minute [0-59], hour [0-23], day [0-31], month [1-12], weekday [1-7] (starting Monday, no ranges allowed on any field)
 cron: 0 0 * * * python midnight_cleanup.py