@GregX
This is often confusing because it has to do with a language feature that exists in C#/.Net but not in Python.
https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/ref
Ref values (or out, which is similar) is explained above. It basically means that instead of the function getting an argument and returning a value,
you first create a reference, then pass it to the function. A value for the reference object is then set_within_ the function, instead of returned. The function may return other values, but the reference (ref parameter) will always be set within it and not returned.
Since this is.net specific, you must use the clr module to create this type of object (typed reference object)
The returned value and ref value are explained here:
http://www.revitapidocs.com/2016/f3112a35-91c2-7783-f346-8f21d7cb99b5.htm
Details on the Ironpython implementation of ref and out (similar to ref) here:
http://ironpython.net/documentation/dotnet/dotnet.html#ref-and-out-parameters
Edit: clarity