Class is an abstract representation of a particular type of object. Object is a concrete instance of a class.
Class is often described as a plan or blueprint for an object, as opposed to the actual object, itself. The same class may be used multiple times within a program to create multiple, distinct objects, each with a different name, but each having the same basic form or structure. Thus, objects are specific and concrete -- as much as anything is concrete within a computer -- and, thereby, come into existence at some specific time, persist for some duration, and then disappear when they are no longer needed. Classes, on the other hand, are the abstract descriptions used by the system to create those specific objects, when it is called upon to do so. they exist, in their potentiality for creating objects, throughout a program.
For example, you might think of the plans for a toolshed or the recipe for a cake as analogous to a class. Then, some particular toolshed, made according to the plans, or some particular cake, made according to the recipe, would be analogous to an object. Such objects are referred to as instances of the class from which they were created. Of course, multiple toolsheds and multiple cakes can be made from the same plan or recipe.
Class. Shows a class as an abstraction that may at some time be instantiated within a program to produce individual objects.
Object. Shows an instance of a class. It has been allocated space in the computer and is associated with a name. It is a "concrete" thing, versus an abstraction.