This event type will be triggered once when we need to retrieve the list of items object and every time when a new object is added to our data as given path. Unlike value, which returns the entire object of that location, this event callback is passed as a snapshot that contains two arguments, which include the new child and previous child data.
For example, if you want to retrieve the data on each new comment added to your post in blogging app, you can use child_added.