The scientific definition of Napalm is a thickening/gelling agent generally mixed with petroleum or a similar fuel for use in an incendiary device, initially against buildings and later primarily as an anti-personnel weapon. "Napalm" is a combination of the names of two of the constituents of the gel: naphthenic acid and palmitic acid. 

The US Air Force and US Navy used napalm with great effect against all kinds of targets to include troops, tanks, buildings, jungles, and even railroad tunnels. The effect was not always purely physical as napalm had psychological effects on the enemy as well. 

Napalm B was used in flamethrowers and bombs by American and Allied forces in World War II. It is believed by some that Napalm B is formulated to burn at a specified rate and to adhere to surfaces to increase its stopping power. During combustion, Napalm rapidly deoxygenates the available air and generates large amounts of carbon monoxide and carbon dioxide. Napalm bombs were used during the Vietnam War.