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Inheritance is an essential feature of object-oriented programming. It allows a class to inherit properties and methods from another class. This helps in reusing the code and makes it more organized. Inheritance consists of two major components: Superclass (parent class) and Subclass (child class). A superclass is a class from which other classes inherit properties and methods, while a subclass is a class that inherits properties and methods from its superclass.

A subclass inherits the following elements from its superclass: 1. Variables: It inherits all the non-private data members (instance variables) of the superclass. 2. Methods: It inherits all the non-private methods of the superclass, including constructors and other member functions. 3. Inner classes: It inherits all the non-private inner classes defined in the superclass.

While inheriting elements from the superclass, a subclass must follow certain rules and limitations: - Private members of the superclass are not inherited directly, but they can be accessed through public or protected methods in the superclass. - The constructors of the superclass are not inherited directly but can be called from the subclass's constructor using the 'super' keyword. - If a subclass defines a method with the same name and parameters as a method in its superclass, the subclass's method is said to override the superclass's method.

Let's have a look at an example to understand the concept of inheritance and how a subclass inherits from its superclass. Consider a simple Java program with two classes: SuperClass and SubClass. ```java class SuperClass { int a = 10; void displayA() { System.out.println("Value of 'a' in SuperClass: " + a); } } class SubClass extends SuperClass { int b = 20; void displayB() { System.out.println("Value of 'b' in SubClass: " + b); } } ``` In this example, SubClass extends SuperClass, which means SubClass is the subclass, and SuperClass is the superclass. The SubClass inherits the variables and methods from the SuperClass. Therefore, SubClass can access the variables and methods of SuperClass, in addition to its own variables and methods. Here's the main class to test our program: ```java public class Main { public static void main(String[] args) { SubClass obj = new SubClass(); obj.displayA(); // Value of 'a' in SuperClass: 10 obj.displayB(); // Value of 'b' in SubClass: 20 } } ``` As we can see from the output, the SubClass is able to access both the variables and methods of SuperClass as well as its own variables and methods. Thus, it demonstrates how a subclass inherits from its superclass.