The former installing to C:\PhoenixOS (or drive of your choosing) while the latter involves an external thumb drive. Installation is straightforward and you're given the option to install the operating system onto a connected disk drive or a 'U-Disk'. This requires booting into Phoenix OS or alternatively running the IMG files as a virtual system. Though not a traditional Windows application per se, its main function is to create a bootable disk so that Android can be run as a dedicated operation system on your PC.
Being a fork of the popular Remix OS, Phoenix OS is a distribution of the Android operating system which allows you to run mobile apps and games on a personal desktop computer or laptop.