iPads and iPhones don’t have file systems you can see, but there are still apps and files eating up space. You can see exactly what’s consuming that limited space and free it up.
Each bit of data on your device is associated with an app. For example, downloaded Kindle eBooks are tied to the Kindle app. Music files are part of the Music app, videos are part of the Videos app, and photos are part of the Photos app.
Read more about: How to Free Up Space on an iPhone or iPad