Properties — Properties describe the characteristics of an object. To use the car analogy that I used in the previous post, a car has characteristics, or properties, like make, model, and color. Often, properties have a single value. For example the make property of the car object might have a value of "Dodge"; the model property might have a value of "Durango"; and the color property might have a value of "Red." Properties can also be objects. These are called "accessor properties" because they access another object. In our car analogy, the car object might have a steeringWheel property that accesses a steeringWheel object, and the steeringWheel object may have its own set of properties, methods, and events.
Methods — Methods are actions that you can take against an object. To continue the car analogy, actions that you can perform with a car might be start, drive, and get a tune up. Some methods return values; other methods require values passed into them. For example, the start method of the car object might return a true or false (boolean value), and the tuneup method might require passing in a date for when the tune up occurs. The values that methods return are called return values; values passed into methods are called arguments.
Note The term "parameters" is also often used to refer to the values passed into methods. The actual definitions of these two terms differ somewhat, but a complete discussion of these differences are beyond the scope of this discussion. I'll explain these terms a bit later.
Events — Events are actions that happen in response to other actions. The car analogy works here, also. For example, the car object might have an event named die to handle the possibility of the engine quitting unexpectedly, or it may have a crash event to handle the possibility if the car is involved in an accident.
Collections — Another part of an object model is collections. Collections are comprised of one or more instances, or copies, of the same object. For example, in the car analogy, a car object might have a tires collection that has five instances of the tire object (with one tire object having the isSpare property set to true).
Variables — In programming, variables are considered temporary storage. The can represent objects or data, such as strings or numbers.