You can use the Create macOS Install Disk command in the DropDMG menu to create an install disk or an install disk image for macOS 10.14. This makes it possible to re-install macOS, install it in a virtual machine, or install it on a different Mac without having to download it again. Additionally, if there are problems with a Mac’s hard drive, you may not be able to boot it and access the installer or recovery partition, but you will still be able to reinstall from the install disk that you create here. You can also use it as an emergency disk to boot a Mac and repair or reformat its hard drive, or to restore from a Time Machine backup.
When updating to a new version of macOS, it is recommended that you create your install disk before running the macOS installer, as the installer may delete itself (which would require you to download it again to create the install disk).