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macOS - Photos - Apple
RaviC01 wrote:
What exactly is a library?
The analog is to a room or building filled with books and other resources, of course. Different libraries have different contents, and are very seldom even using the same design plan. Here, the analog is to file system storage filled with photos and videos.
Is it a directory created in the file system on Mac?
Technically, yes, it’s a file system path. A subdirectory of your home directory, and further subdirectories of that. There are other parts of the file system used for some aspects of Photos storage and access, when enabled.
Pragmatically, you don’t need to know much more than its existence; that you have a library.
If you really want to know more about the Apple file system:
File System Basics
And note: macOS goes to some effort to protect itself against malware, corruptions, and the inquisitive users trying to write or modify or delete data where they probably shouldn’t; what’s called System Integrity Protection. Put differently, whole sections of the file system are protected against modification. There are fewer protections in your own home directory, and corruptions and deletions can occur.
It says the default system library for Photos is in the Pictures directory. Why don't images stored in the Pictures directory via Finder, appear in the Photos app?
Because viewing files through a generic file-viewing tool gets awkward for users, mostly. It clutters up Finder with tools and controls used for several file types. Or it makes Photos do piles of stuff that it’s just not going to be good at.
Also, when I import pictures from my Downloads directory into my Photos app using Finder, is a second copy of that photo created in the Photos app instead of actually moving the pictures from my Downloads directory into the Photos app?
Use the provided tools within Photos to import and to consolidate the photos and videos, and let Photos manage its own storage, and let it index and search its library as needed.
If you want the level of control you’re exercising here (moving files around, copying stuff into areas used by apps from Apple and third-party vendors, you’re probably best served using Linux. (I don’t mean this to be flippant, either. Apple has strong opinions on how a computer should work, and it gets… difficult… to work across those opinions while working with Apple products.)
Where exactly are the images stored when they are stored in the Photos library? Why do they not appear in the Pictures directory in Finder when it is the System directory for Photos?
Photos manages its own storage, both locally, in local caches elsewhere within the file system, and in iCloud when iCloud Photos is enabled.
Since you want to to understand app-internal organizations, I’d recommend creating and using a completely different macOS login for your experimentation, and so long as you perform your tests and modifications within your login directory and its subdirectories (and a login-specific Apple ID if you want to use iCloud services during your testing), you won’t corrupt much outside of that. Use the Apple tools and controls within your main login.
