How does Restore Pictures App work?

I downloaded an app to restore deleted pictures. That worked too. There are many deleted photos in the app, but also photos that I have never seen before. But how does it work that the app recognizes the deleted pictures on my Huawei smartphone even though they have been deleted. They are not in my Recently Deleted folder. The cell phone then has to save the deleted files somewhere. Where can you then delete them again?

If you are an Androis user, deleted data will be moved to the trash, so you don't need an app.

This is probably why this app finds your deleted photos.

You just because you delete a picture does not mean that the pictures are gone forever they are saved on your mobile phone under a folder I have no idea the app only has to examine this folder and the pictures are there again pictures are not for always deleted it silk you reset your mobile phone completely or the sim card then all pictures etc are gone

And where can I find the trash can?

Click under the gallery menu with 3 points and select the recycle bin there.