This is another commonly used way to distribute applications for macOS; the corresponding disk image files generally have the .dmg file extension. They can be used as a mountable disk or volume for storing files of various types. The native format used for this nowadays is Universal Disk Image Format (UDIF), prior to that, New Disk Image Format (NDIF) was used. It also supports compression and encryption. Instead of using a header, most of them can be recognized by the trailer, which contains a magic four-byte koly value at its start.
In order to get access to files inside, the disk image can be mounted or converted using standard tools bundled with Apple operating systems, such as the hdiutil console. On other operating systems, it is possible to use tools such as dmg2img to convert these files into a non-proprietary disk image format and then mount them as usual. Alternatively, they can be unpacked using tools such as 7-Zip.