Abstraction, inheritence, polymorphism and encapsulation are object oriented concepts. These are explained here in detail with examples.
Encapsulation or Modularization is an important concept in object oriented paradigm. Details of encapsulation are explained here.
Polymorphism is multiple forms. What does it means? How to implement it? What are advantages and disadvantages of polymorphism?
Inheritance is can be called as core of object oriented programming. This article explains details of it with code example and UML diagram.
Abstraction is an important concept of object oriented programming. This article explains details of abstraction with UML and code examples.