Backbone.sync is a function that is called every time when Backbone.js tries to read or save a model to the server. It is used to display the state of the model.
method: It specifies the CRUD methods i.e. create, read, update and delete.
model: It specifies the model to be saved or collection to be read.
options: It displays success or error message depending on the method succeeded.
Let's take an example.
See this example: