An object is an instance of a class. You could think of a class as the description of a concept, and an object as the realisation of this description to create an independent distinguishable entity. For example, in the case of the Television, the class is the set of plans (or blueprints) for a generic television, whereas a television object is the realisation of these plans into a real-world physical television. So there would be one set of plans (the class), but there could be thousands of real-world televisions (objects).

Objects can be concrete (a real-world object, a file on a computer) or could be conceptual (such as a database structure) each with its own individual identity. Figure 1.3, “The Television objects example.” shows an example where the Television class description is realised into several television objects. These objects should have their own identity and are independent from each other. For example, if the channel is changed on one television it will not change on the other televisions.

Figure 1.3. The Television objects example.