In Windows 10, the Pictures library has a folder called Camera Roll. The Camera Roll folder is created by the Camera app. Windows previously didn’t have a dedicated Camera app but as of Windows 10, that has changed. All the photos you capture via the Camera app are saved to this folder.
Phototheca automatically imports all photos from this folder and shows them in the Library under the “Camera Roll” item. This is a built-in auto-populated Album that doesn’t allow you to change its content, and it always reflects the content of the same Windows 10 folder