So far, we’ve been defining variables as instance variables in our Java classes. Instance variables are just variables defined inside a class, and every instance of a class can have a different value for an instance variable. In this module, we’ll look at defining static variables in our Java classes. Static variables are also defined as variables inside a class, but with the keyword 'static'. Static variables have the same value for every instance of a class. In fact, you don’t even need to create an instance of a class to use a static variable! We’ll also look at static methods. And just like static variables, you don’t need to create an instance of a class to use, or call, a static method. In this module, we’re also going to introduce polymorphism, which refers to overloading and overriding. We’ll focus on overloading, which is having two or more methods in the same class, with the same name.