Are both "sync" and Backbone.sync events related in some way - what's the difference between them?

There is no connection between them, although both are related to the task of synchronizing data with the server.

Backbone.sync implements the persistence strategy used by your Backbone.js application. If you need to change something about how your data is stored, you can override the default implementation. Most people shouldn't worry about this, but if you have to, you can check How to Override Backbone.sync?

Synchronization event indicates that the model update was successfully synchronized with the server. Like other events in the model, it also goes into the collection. This happens when:

• Save the model successfully .
• Successfully destroy the model.
• Successfully creating a model in the collection.

Note . Prior to v0.9.9, the sync event was not guaranteed - if you declared a successful callback during any of these operations, the sync event will not be fired.