An instance variable is a variable that is associated with a particular object , each instance of the class will have its own copy of each of these variables.
A member variable is associated with the class, and is shared by all objects of the class. It is also referred to as class variable because the variable belongs to the class, not to any particular object.
here's an example I found:
public class Sphere
// class variable
static double PI = 3.14;