Dragons were the original Firebenders but then they taught the Sun Warriors firebending.Firebending is the most aggressive and destructive of the four bending arts but zuko understood that it was more than that as it was shown in the "Firebending Master". Firebenders use kicks and punches to make various shapes of attacks. While Jabs and punches make small fireballs and flamethrowers. Spinning kicks create Rings of fire. When multiple Firebenders attack at once, they combine energy that enables them to produce missiles of flame that can travel long distances. Firebenders weapons are spears and Swords.
Blue firebending is an advanced technique of Firebending. Princess Azula usually used this move to stuck Aang. Blue fire is much hotter than the normal red and orange flames. Blue fire can shatter solid rocks with fireballs. It can also slice through different kinds of solid objects. Master Firebenders, such as the Dragons Raan and Shao they can breathe flames. The Breath of Fire is related to how Dragons breath fire. They said that they use the Breath of Fire to get warm in extreme cold. Combustion is when Firebenders us firebending to cover themselves in flames. The last type of Firebending is lightning. Only Firebending Masters can generate a lightning. A lightning can explode a whole boulder into pieces.
When you disrespect a Firebenders command you are challenged to an Agni Kai(Zuko was in an Agni Kai between his Father). Among Firebenders or upper class Firebenders conflicts or disrespect of honor are settled an Agni Kai.