Ну, поскольку речь идет о конкретном определении из OOAD by G.Booch, то можно у него же и посмотреть определения для составляющих данного определения:
📝 "Class - A set of objects that share a common structure and a common behavior. The terms class and type are usually (but not always) interchangeable; a class is a slightly different concept than a type, in that the former emphasizes the classification of structure and behavior.
Type - The definition of the domain of allowable values that an object may possess and the set of operations that may be performed on the object. The terms class and type are usually (but not always) interchangeable; a type is a slightly different concept than a class, in that the former emphasizes the importance of conformance to a common protocol.
Object - Something to which you can do things. An object has state, behavior, and identity; the structure and behavior of similar objects are defined in their common class. The terms instance and object are interchangeable.
Instance - Something to which you can do things. An instance has state, behavior, and identity. The structure and behavior of similar instances are defined in their common class. The terms instance and object are interchangeable.
Identity - The nature of an object that distinguishes it from all other objects."
- "Object-Oriented Analysis and Design with Applications" 3rd edition by Grady Booch, Robert A. Maksimchuk, Michael W. Engle, Bobbi J. Young Ph.D., Jim Conallen, Kelli A. Houston