Object - A real world object is an entity which can be distinctly and precisely identified and described. A real world object is characterized by a set of attributes and a set of behaviors
Object - An object in a software system is an instance of a class defined by an identity, a state and a set of behaviors.
Class - A real world class is a set of objects which have similar states and behaviors.
Class - A class in a software system is representation of an abstraction or model of a real world entity in a software language.
Class - A class in a software system implements the states and behaviors of a set of object instances. A class in a software system is a template for creation of instances objects. Attributes map to fields or instance variables, behaviors map to methods.
Note that we have used “class” and “object” in multiple different ways.