You can describe a Python function in words by putting triple quotes at the top, so that appears in Help. Is there a way to do that in Mathematica?
You can add comments anywhere. You can also create usage messages for your functions.
(* comments are enclosed in these kinds of braces*)
MyFunction::usage = "This is how to define a usage message for MyFunction"
You can see the usage message with Information (for example):
Information[MyFunction]