An object is self-contained component properties and methods needed to make a certain type of data useful. An object's properties are what it knows and its methods are what it can do. Objects are the fundamental building blocks of applications from an object-oriented perspective. An object consists of data and functions, functions are used to perform the operations on data. Each object is capable of receiving messages, processing data, and sending messages to other objects.
A class is a collection or group of similar objects that have some properties, common behavior, and relationships. Objects with similar properties and actions need to be grouped together into a unit that can be used in a program. Each class describes a set of individual objects. Each class should be designed and programmed to accomplish a task. Example of class: class of persons, class of animals, etc.