The central file in Lightroom that is critical to understand and properly maintain is the catalog. The catalog is a database that stores the location of your images as well as all adjustments that are made to your images. Adjustments are not applied to the image, but rather stored in the catalog. Lightroom reads the catalog and applies the adjustments to the image when it is displayed in Lightroom. The original image is never changed. That is why there is no "Save" button or menu option. Adjustments are stored in the catalog as they are made. Consequently, it should seem obvious that the catalog must be backed up on a regular basis. If you change the name of an image in Lightroom, Lightroom will understand and the changes will still be applied to the image. However, if you try to rename the image outside of Lightroom then the changes will be lost because Lightroom will no longer know how to associate the changes with the image.
In order to share an image with all of its adjustments with someone else, another computer, or send to a lab, it is necessary to export a copy of that image. That exported image will contain all of the adjustments that have been made using Lightroom.
Because of this unique way that Lightroom works, it is impractical for you to think you can manage your image collection using Finder. You can create collections that can be shared via Lightroom mobile and made accessible on all your devices. But you cannot expect to manage your image library using Finder. If you try to do so, you are really going to cause confusion and frustration for yourself.
Lightroom saves the changes you make in the Catalog.
You can Export the File you have made changes to from File>>Export
Refer the link below to know how catalog works
Hope that helps