How does storage work in lightroom

Lightroom Classic works with its “imported” files the same way that page layout and video editing applications have worked with their files for decades, the same way that a web browser loads media on a web page: The files are not actually stored by the application, but are linked via a folder path to a file system location. In other words, if you know how traditional “referenced” file paths have worked since the DOS days, then you already understand how Lightroom Classic works with original files. The originals can be spread across any number of folders or volumes, even unmounted volumes such as hard drives that aren’t currently connected. Because all Lightroom Classic needs to know is the path to each file.

The Lightroom Classic catalog is a traditional SQL database. It stores only edits to individual images and collections of images. When you edit an image, the edit metadata is stored not with the original but in that database (although there are options to store it other ways). This allows nondestructive parametric editing, which in modern apps is much more the rule than the exception.

Original files are stored separately as noted above, and you can instantly locate them in your normal file system using the commands dj_paige mentioned. The expendable preview cache is also stored separately. If you want a finished version with the edits baked into the file, you export it…again, similar to using a traditional video editor.

So really, the way Lightroom Classic works it not new or different, it only seems different compared to applications like Photoshop and Word where you open one document at a time in its own window.

For the cloud, Lightroom Classic is focused on the local file system so it doesn’t store images in the cloud by default. If you want cloud access to an image from other devices, you enable cloud syncing for that image (or an entire collection). What is synced is not the original, but a bandwidth-efficient Smart Preview (compressed DNG-based proxy) that can sync any mobile edits back to the Lightroom Classic original.

If you want to store all originals in the cloud you have to use cloud-based Lightroom (not Classic), but to support full cross-device cloud capabilities, Lightroom stores files differently where you don’t have local file system access to the originals.

Lightroom Classic (you don't say you are talking about Classic, are you?) does not store your files. All of your photo files are stored on your hard disk(s) somewhere, wherever you put it or wherever you told Lightroom Classic to put it. They are right there on one your disk(s) for you to view/use whenever you want. If you have the LrC application open, you can find out where LrC thinks the photo is in the metadata panel, or by right-clicking on the photo and select "Show in Explorer" (Windows) or "Show in Finder" (Mac).

As far as the other items you mentioned ... cloud copies are stored in the cloud, and you can't really access them other than via the software LrC or via a web browser with proper link. You also mention "Changes in files copied" but I don't really know what that means. If you are talking about your edits, they are stored in the Lightroom Catalog file, and you cannot access them any way other than via the LrC software, there is no such thing as a file system to help you find your edits. Optionally, your edits can be stored in both the Lightroom Catalog file and an xmp file (or the xmp portion of a file), in which case you can access them outside of LrC, but again there's rarely a need to do so.

I think it would be wise to not worry about DOS here, and use Lightroom Classic to access/manage your photos and your edits. I note that if you choose to access the files via your operating system, you will NOT see your edits. The edits do not result in changed pixels in your image files, and so if you were to use some other non-Adobe app on your computer to view these images, you will not see your edits. You will get the most out of LrC by using its features to access/manage your photos and your edits, rather than using operating system methods.

The only "DOS-like" information you really need to be aware of is what folder your LrC catalog is in, what is the parent folder where your photos are stored, and what folder backups are written to.