Possible duplicate:What is the difference between an instance and an object?
What is the specific difference between an object and an instance?
An object is an instance of a class.
When you instantiate a class, the result is an object of type class.
In short, an object is a software bundle of bound state and behavior. A class is a project or prototype from which objects are created. instance is the only and unique division of a class.
Read this article: Class vs Object vs Instance