Well, there’s quite a lot, as it happens, and it affects the way you store, access and organize your photos
Managed images
Some photo organising applications copy your photos into a dedicated image database which is inaccessible to other programs. It sounds restrictive but does have some advantages, in that images are less easily lost or 'disconnected' from the database.
Examples include Apple Photos, the now-discontinued Apple Aperture and Capture One's 'Managed' catalogs.