How to create item in DynamoDB using Android?

I have an android app connected to AWS Amplify and I have been trying to add user data to a DynamoDB database

Amplify.DataStore.save(
                            item,
                            { success -> Log.i("Amplify", "Saved item: ") },
                            { error -> Log.e("Amplify", "Could not save item to DataStore", error) }
                        )

This is the code I have so far, item is a user object containing user data. I'm not sure whether data store only stores data locally or whether it stores it locally and on the cloud

Could someone point me in the right direction?