Deeply nasty and indiscriminate incendiary weapon usually delivered from the air.
Has its roots in Greek fire which was the fuel in burning-liquid weapon (sort of like a large supersoaker that sprayed liquid fire) used by the Byzantine Empire around 670AD. A large siphon (exact details are hazy) would be mounted in the bow of a warship and used to hose enemy ships. Used in naval battles since it could continue burning even on water.
First created in 1944 by the US, it has been used all over the world as it has a big psychological effect on the recipient. Napalm is usually a mixture of petrol with something to thicken the liquid to give a better splatter effect.
Modern Napalm is primarily a combination of benzene and polystyrene known as napalm-B generating temperatures of 800 to 1,200 degrees Celsius (water boils at 100'C).
Probably replaced now with more sophisticated FAE (Fuel air explosion) ordinance.
"I love the smell of napalm in the morning... It smells like... victory."
- Apocalypse Now, Colonel Kilgore.