Class vs Object vs Instance

Class

A Class defines the structure, property, and behaviour of an Object. You can think of a Class as a blueprint. Exactly like building a house, you use a blueprint to create a particular model, maybe a 3 bedroom detached dwelling. You would have a different blueprint for a 5 bedroom dwelling for example. Its the same with Classes in their simplest form, you could define a Class representing a 3 bedroom dwelling, and another Class that represents a 5 bedroom dwelling.

Object

An Object is created from a Class, like a house is created from a blueprint. You could use a blueprint of a 3 bedroom home to build multiple 3 bedroom homes - 1 blueprint to create multiple 3 bedroom homes. This is what happens with a Class. You can create multiple Objects from your single Class - remember, a Class is just the blueprint for creating Objects of the same type.

Instance

So we've taken our blueprint (Class), and created multiple 3 bedroom homes (Objects), but how do we refer to one particular home (Object) we've built? We refer to a particular Object as an Instance. If I were to paint the frontdoor of one of the homes, I would be painting the door of a particular Instance of the Objects (home) created from my Class (blueprint).

This is a very simplistic model but I hope it helps.