The text says the following:
In Python there is a value called None, which represents the absence of a value. None is the only value of the NoneType data type. (Other programming languages might call this value null, nil, or undefined.) Just like the Boolean True and False values, None must be typed with a capital N.
This value-without-a-value can be helpful when you need to store some-thing that won’t be confused for a real value in a variable. One place where None is used is as the return value of print(). The print() function displays text on the screen, but it doesn’t need to return anything in the same way len() or input() does. But since all function calls need to evaluate to a return value, print() returns None. To see this in action, enter the following into the interactive shell:
>>> spam = print('Hello!')
Hello!
>>> None == spam
True
Behind the scenes, Python adds return None to the end of any function definition with no return statement. This is similar to how a while or for loop implicitly ends with a continue statement. Also, if you use a return statement without a value (that is, just the return keyword by itself), then None is returned.
I think I understand what None is, but I am not understanding the code. Why is it that spam is then equal to None when it was assigned to be print('Hello!')? When I enter spam into the interactive shell immediately after the assignment it returns nothing. I get a feeling it is because the argument Hello! is immediately forgotten when print() is called and returns a value, but if I have defined spam to be the print() function with the argument Hello! passed through should it not always return Hello!?
To add to the comments and be more clear, your print() function printed 'Hello!' to the screen and returned None to the program. Printing and returning are not the same thing--printing is for the user, returning is for the program. The print goes to the screen only and (usually) cannot be further used by the program. The returned value can be stored in a variable, such as spam, and used further.
The distinction between printing and returning is important enough that the Python standard is that if a function prints something it should not return any value other than None, and if the function returns a value it should not print anything. This standard is not followed by many other languages (most notoriously C) and is not consistently followed in Python, but this distinction does help the clarity of Python. If you want to study this concept further, do a search on "side effects" in programming.