Class vs Object — What's the Difference?

A class is a blueprint that defines properties and behaviour; an object is a concrete instance created from that blueprint. One class can produce many objects, each with its own data.

The concept

Think of a class as a cookie cutter and objects as the cookies. The class says what fields and methods exist; each object stores its own values.

Creating an object is called instantiation and usually uses new or a constructor.

One class, many objects

Each object has its own state.

Practical examples

JavaScript

class Car {
  constructor(color) { this.color = color }
  honk() { return this.color + ' car says beep' }
}
const a = new Car('red'), b = new Car('blue')

Python

class Dog:
    def __init__(self, name): self.name = name
    def bark(self): return f'{self.name}: woof'
d = Dog('Rex')

Static vs instance

class Math2 { static pi = 3.14 }  // belongs to the class
new Car('x').color                 // belongs to an object

Common mistakes

Using the class name when you mean an instance.
Storing per-object data in static fields.
Creating objects without initialising required fields.

Key takeaways

Class = blueprint, object = instance.
Many objects per class.
Static members belong to the class.

FAQ

Do all languages have classes?

JavaScript historically used prototypes; class syntax is sugar over them.

Can an object exist without a class?

Yes in languages with object literals, such as JavaScript.