Basically older Programming language like COBOLT and C followed the Procedural Programming approach.in this type of programming language only focus on the logic rather than data abstraction.
Modern programming language like C#,python, Cpp and java etc. follow the Object oriented approach.
Object Oriented programming is main focus on the data rather than just write the instruction to perform the task.

the class are user define data types
and in simple word object is variable of that data type that can store the desire things.

• class is blue print for the creating the object, and A class can define the attribute and behavior. for example:-- if we are design the car in our application then we could define attributes of the car like model ,fuel, and behavior like start ,break , accelerate etc.. this attribute and behavior not specific for a one model.

Abstraction

Abstraction is focus on the what object can do in stead of how object can done.
In the abstraction we can only know essential features without knowing the detail background implementation
abstraction is important when we do any modification in one module than no other module can be affected_
example
break in car we only use this functionality and not know mechanism behind this functionality
or we also say same as accelerator

Encapsulation

encapsulation is closely related to abstraction.
encapsulation bind the data and behaviors together in a single unit

Abstraction is implementation hiding.
Encapsulation is information hiding.
Abstraction provide generalization and hiding their implementation.
Encapsulation is hiding of internal data from outsider.

Inheritance

inherence is powerful features of the oops
inheritance help to organizing the class in hierarchy and enabling these class to inherit attribute and behavior from class above in the hierarchy

Inheritance is concept that allow us to create new class from from existing class by inheriting the properties of that class

Some Advantage of inheritance:

Reusability ,Flexibility ,Redundancy ,Data hiding

• Single inheritance
• Multi-level inheritance
• Multiple inheritance
• Multipath inheritance
• Hierarchical Inheritance
• Hybrid Inheritance

Polymorphism