What is "instance-variables"

An instance variable is any declared variable within a class, but outside a method or constructor.

Instance variables are initialized with the default value every time a new instance of the class is created, even if they later receive an explicit value right after the constructor of the object is executed.

Follow an example using java:

public class UmaClasseQualquer {
   //Qualquer variável declarada nesse espaço é uma variável de instância...

   int VariavelDeInstancia;

   public static void main(String[] args) {
      {...}
   }
}