In Java, the `static` keyword is used in the context of a class, rather than an instance of a class. It pertains to members of a class, specifically variables and methods. 1. `Static` Variable: A static variable is common to all instances (or objects) of the class because it is a class level variable. This means there is only one copy of the static variable, regardless of how many instances of the class exist. So if you modify the value of the variable in one instance, the change is reflected in all other instances. 2. `Static` Method: Like static variables, static methods are also tied to the class itself, not any particular instance of it. Consequently, you can call a static method without creating an instance of the class. They can only manipulate static variables and can't interact with instance variables. As for when to use it: If you have a variable that's not tied to an instance of a class and its value is consistent across all instances, it should be made static. This can improve space efficiency because only a single copy of the variable exists. Similarly, any function that doesn't use instance variables can be made static. Example: ```java public class Car { static int numberOfCars = 0; // This is a static variable public Car() { numberOfCars++; // This will increase for every new Car object created } static void displayCarCount() { // This is a static method System.out.println("Number of cars: " + numberOfCars); } } ``` In this example, `numberOfCars` is a static variable that increments each time a new `Car` object is created. `displayCarCount()` is a static method that displays the current count of cars. Both are tied to the Car class, not any specific instance of Car. We can call `displayCarCount()` without creating a Car object: ```java Car.displayCarCount(); // prints "Number of cars: 0" ```