This is called the Aviation Firestarter simply because it has been standard issue in USAF Pilots survival kits for years, it is a very simple but very effective design and sits very well with our "If it ain't don't fix it" policy
It is a magnesium block with a sparking flint embedded within it, simply shave off some magnesium and light with the flint. Magnesium burns super hot and will get your kindling going easily.
Anything the US Military stick with for Donkey's years has to be really reliable and a trusted piece of kit.