Class: Class is a blueprint or a set of instructions to build a specific type of object.
Object: Object is an instance of a class.

Generally class consists of constructor, data and methods.

Constructor a special method (same name as class) used to instantiate (create) an object of class.
Date stored State variable / Data Member / Property of that class
Actions performed Method / Behaviour / Function of that class

Example:
Class:  Car
Objects: Mercedes, BMW, Toyota
Data Member: Price, Speed, Wheels, Mileage, Model, Colour
Member Function: brakes(), accelerate(), start(), stop()

Four pillars of Object Oriented Programming:

  1. Abstraction
  2. Inheritance
  3. Encapsulation
  4. Polymorphism

Do a SOLID check whenever creating a class.