Merge pull request #100 from hjwp/patch-1

distinguish operators and functions

python_introduction/README.md

@@ -89,7 +89,8 @@ OK, enough of strings. So far you've learned about:
 
 - __the prompt__ - typing commands (code) into the Python prompt results in answers in Python
 - __numbers and strings__ - in Python numbers are used for math and strings for text objects
-- __functions__ - are actions in Python. You've used both English-language functions (upper(), len()) and symbolic ones (+, *).
+- __operators__ - like + and *, combine values to produce a new one
+- __functions__ - like upper() and len(), perform actions on objects.
 
 These are the basics of every programming language you learn. Ready for something harder? We bet you are!