You will be able to temporarily store data on your computer when, for example, traveling in areas with no internet connection. The data will be uploaded to the Narrative Service and then processed at the next sync (when you have an internet connection again). This is all automatic as long as you have the checkbox "Narrative Service" ticked in the Narrative Uploader.
Local storage is also an option, by ticking the box "Save copy to hard drive". Please note that in order to transfer photos locally you will need to sign into the Uploader with an internet connection. Once signed into the Uploader you can transfer photos locally without an internet connection.