Need  for object-oriented paradigm

• it produces reusable code/objects because of encapsulation and inheritance.
• the data is protected because it can be altered only by the encapsulated methods.
• it is more efficient to write programs which use pre-defined objects.
• the storage structure and/or procedures within an object type could be altered if required without affecting programs that make use of that object type.
• new functions can easily be added to objects by using inheritance
• the code produced is likely to contain fewer errors because pretested objects are being used.
• less maintenance effort will be required by the developer because objects can be reused.

Encapsulation
It is the combining of data items (or attributes / properties) with procedures (methods) for manipulating those data items, into a single unit called an object. 
Object
An object consists of a data structure plus a set of procedures for manipulating that data structure. The data can be manipulated only by those procedures contained within the object. 
Class (Object class / Object Type)
A class is a template defining a set of objects which share a common data structure (set of attributes / properties) and a common behaviour (set of methods). 
Inheritance
Inheritance is a relationship among classes/objects wherein one class/object shares the structure and/or behaviour defined in one (single inheritance) or more (multiple inheritance) other classes/objects. 
Polymorphism
Polymorphism is the ability of an inherited class to customize an inherited method.  Two different classes may inherit a particular method from a common parent, but they may re-define it in different ways.