That notation gets to the very essence of what "passing by value" and "passing by reference" really mean. You could say there is really no such thing as "passing by reference" and everything is "passed by value", by which I mean to say that all function parameters are passed the same way--they are copied for the function. Typically, C++ texts will make a big point of the differences between "passing by value" and "passing by reference". They will give an example of "passing by value" similar to this:
Also, I've seen this, which is really confusing me: int*& var, for example, usually as a function parameter. What does *& mean?