FineReader PDF for Mobile is powered by ABBYY Neural Network that automatically analyses the photos in the phone gallery and sorts images. It works on-device, so you don`t need an internet connection for the classification. Photos are not sent anywhere for the classification and recognition processes. 

You can find more information about the classification in the following articles: 

How long does it take to classify photos? 

What types of images are used in classification?

What is the accuracy of the classification in FineReader PDF for Mobile?

How to improve classification search results

Why do I receive such broad search results in classification?