App bundles are folders with a file extension and a binary at a specific place. Folders that you can double click (and then some!) That's pretty great. DMG fil

App bundles are folders with a file extension and a binary at a specific place. Folders that you can double click (and then some!) That's pretty great. DMG files are a way to ship app bundles (or other files). They're basically images with compression and checksumming added on top (I think). Images are useful (compared to, say, a zip archive) because you can mount them (e.g., over a network). That's useful for all kinds of sysadmin-y things. (Compression and checksumming are obviously useful as well.)