Each uploaded Photo exists just once in your account in the Photo Library. The Photo Library gives you access to all Photos uploaded into your account. Once a Photo is in your library, it can be placed in as many albums as you like. Each Photo Album calls up an instance of the singular Photo in your Photo Library rather than making a duplicate of it.
When you delete a Photo from a Photo Album, the Photo is removed from the album but still exists in the library (and any other Photo Albums in which it was inserted. When you delete a Photo from your Photo Library, it will be moved to the Photo Trash Can where it will stay until it has been there for 30 days. After that time it will be permanently deleted.
Deleting Single Photos
Deleting Photos in bulk
If you have several Photos you want to delete at once, you can use the “Delete Photos” command that is found at the top of your Photo Library. You will first need to click on the check box next to the photos you want to delete in your library. Once you have done that, you can click on the brown “Delete Photos” link. Follow the steps in the image below: