Napalm is substance, that, when mixed with gasoline, produces an incendiary gel. This gel is capable of sustained burning at high temperatures (Up to 1200 Degrees Celcius), for fairly long, and can stick to many surfaces. Against soft targets, such as infantry, napalm causes serious injury or death. Even garrisoned forces are in danger, as napalm can quickly burn up the oxygen in enclosed areas to cause suffocation. However, vehicles are to a degree flame resistant, and can withstand prolonged exposure.
Napalm was invented in World War I, as pure gasoline flamethrowers splashed and drained their fuel tanks to easily. Various gels were used to mitigate these problems, and the Napalm additive proved to be the most effective and efficient.
During the Great World War II, Soviet forces used napalm as a fuel in both their Flame Towers, and in the fuel tanks of their flamethrower infantry. The Soviet flamethrowers shot out a highly pressurized ball of napalm. Upon hitting a surface, splattering would occur, blanketing the immediate area in deadly flames. However, as the flamethrower did not launch a sustained stream, there was a slim, but still significant, possibility of avoiding injury by running away, escaping the blast radius. Also, the highly pressurized fuel had a nasty habit of exploding if the flamethrower tanks were ruptured, which was quite dangerous to friendly units in formation with a flamethrower.
In the First Tiberium War, both GDI and Nod utilized napalm. Nod adapted old Soviet designs for new flamethrower infantry. These troops had wider angled nozzle, allowing for a continuous stream. The splattering effect was gone, however, and due to the wide angle of the thrower, friendly units in the vicinity were endangered when next to the infantry. Nod also fielded larger versions of their flamethrowers on Flame Tanks. GDI equipped their A-10 Thunderbolt II aircraft with napalm bombs, which would erupt in a large inferno upon hitting the ground.
After the war, GDI recalled these weapons, and abandoned flame weaponry altogether. Nod continued to use flame tanks, and equipped it's Black Hand troopers with advanced flamethrowers, making them some of the best Urban Combat forces on Earth. True napalm was replaced by Tiberium-derived gels, which increased safety. However, the mixture is still colloquially referred to as napalm.
Napalm is still used by the Black Hand and Flame Tanks in the Ascension Conflict.