What does the "m" stands for as a prefix to the variable? Craig said member? What is it for?

The m for member is a naming convention, and isn't needed for the code to work. However, it will make the source code easier to understand, as a member variable is one that limits it's scope to the class that it's in. Member variables are therefore made private for the most part, so they are working parts of the object not exposed to the outside world. Think of a radio, and how there's a lot of parts inside a radio that the user doesn't need to know about, that are inside the radio in order for it to work. The m in front of the member variable helps us remember that this value can only be accessed inside the object, like a transistor inside a radio.