Lightroom 5 came out of beta today and is now available for pre-order from B&H (available by June 13th, download available now)One of the new features is Smart Preview - this nifty features frees laptop owners to keep originals on an external disk but still work with and edit copies when you are on the road and not connected to that drive.  It does this by creating a lossy DNG file that is stored on your laptop, typically they are about 5% of the size of the original images with a maximum dimension of 2500 pixels.  You can star/rate, add keywords and other meta data AND edit in the develop panel. You can even export a file up to 2500 pixels, perfectly large enough for sharing online.    More in the video below.Note about Catalogs- A catalog is a database that tracks the location of photos and information about them, you can have more than one catalog but only one catalog can be open at a time.  I typically have a catalog for each year, starting a new one at the beginning of each year.  Catalogs do not actually store your photos, just the previews and the changes you have applied, along with any metadata.  The actual images are stored in folders on your hard drive or multiple hard drives.