How Change Events Are Triggered In Backbone

I was having trouble understanding the various states that a given Backbone model, and all it's attributes, might be in. Specifically, how does an attribute change, and trigger the change event for that attribute. The change event isn't triggered when the model is first created, which makes sense because the model had to previous state. In other works, creating the model also creates a state machine for the model attributes. However, this can be confusing if you're adding a new attribute to a model.