the structural similarities between firefox os and android allow the mozilla platform to run on a number of devices that ship with android. while some ports of firefox os are hardly different from their original versions, others are heavily modified to fit the device in question. there are quite a few to note that are specifically made for firefox os as stated above. there are some that are designed for the developers themselves and others that are consumer-phones. there are also emulators for testing both apps and the os itself on the desktop which are designed for both os testing and the developers themselves.