In Scheme you have a nice little garbage collector so you don't have to worry as much about these kinds of problems. Classes can also have their own variables. They are known as Class variables which seems like a fairly good name for them. Instance variables would be the variables that each object has for itself. Class methods are functions that apply to the entire Class of Objects.
Instance methods belong to each function.
In a Stack Class a Class variable could be the number of stacks that have been created and a method could simply be a function returning this value. An instance variable would be the list for each stack and the instance methods would be push, pop, and so on. Speaking of stacks and classes, you will see more of them in Exercise 3. In this way we have a function which, when called with no arguments, returns a new object with specified state and methods. Any object created by bankobject-maker will have the same class.