The order of the photos in an album is important: when you create slide shows, books, or Web photo galleries, iPhoto presents the photos in the order in which they appear in the album.
Once you’ve created an album, you may want to fine-tune the order of its photos.
Removing a photo. Don’t want a photo in an album after all? Select it and press the Delete key. This removes the photo from the album, but not from your hard drive or photo library.