The Disk Image format has been around on the Mac for a really long time. It is a great way to store and/or send large amounts of information. You can save several files and folders into one Disk Image for emailing, storage or whatever. Disk Images are also good for securing private information because they can be encrypted with a password. Besides the Disk Utility App, there are third party Apps that do this for you, for some money of course. This article’s detailed explanation of how to create Encrypted Disk Images with Disk Utility is helpful, although a bit technical.