Adobe Photoshop Lightroom is a catalog-based post-processing and image management software. For someone new to such photo managing approach it may sound complicated at first. Simply put, a Catalog is a Lightroom-specific database file. Employing a database system means Lightroom does not work with the original files directly. Instead, it stores information about them – along with rendered previews – in a set of files that make up a Catalog. The list of such information includes metadata, filters, rating and adjustments you may have applied to a specific photograph inside Lightroom. The actual image file is not stored within the Catalog, only information about the adjustments and an image preview. Image files themselves remain wherever you decided to put them in the first place before importing into Lightroom. As a result, whenever Lightroom prompts you to back up your Catalog, it does not back up the actual images. Only the relative information stored in that Catalog is copied.