Fire
Fire has been mankinds greatest tool since memory serves us. Humans utilized fire in many ways. To keep them warm, heaten their food, to have a source of light at night or simply to keep strange creatures away.
In the life of Ninja:
Fire is one of the basic 5 Nature Elements. the other 4 being Water, Wind, Earth and lightning. Fire is more commonly known as Katon (火遁).
Fire attacks are mainly begin with gathering chakra in the stomach, and unleashed through the user's mouth. The ultimate fire attack is Amaterasu. Being the ultimate fire attack, it can burn everything, even other, normal fire. It's still not clear wheter Amaterasu is actually a Blaze or Fire technique, but either way, it's a devestating technique.
Fire is obviously weak against water. This is a common fact and this is also so in Nature Manipulation. Water simply extinguishes fire.
On the other hand fire is very strong against wind. If an opponent uses a wind attack against you, while you retaliate with a fire attack, the wind attack will backlash and strenghten the fire attack, causing your fire attack to be increased in strenght and finally harming the opponent.
there are a lot of people in the Anime / Manga who have a fire element as primary/secondary, so it's presumable to say that it isn't a rare element. 3 Canon users would be: Sasuke Uchiha, Itache Uchiha and Hiruzen Sarutobi.
In terms of tactical use, fire can be very handy. It can heat up the atmosphere to enhance lightning based attacks or even generate Rain clouds. (As seen in the Sasuke/Itache fight) but it can also burn the invironement. It can melt things and even evaporate water to some degree. Sometimes, Fire attacks are also used to harden certain earth attacks, or create meteors.
Other than that, Fire is at the base of various Kekkei Genkai such as:
Blaze Release (炎遁)
Scorch Release (灼遁)
Lava Release (熔遁)
Boil Release (沸遁)
does this suffice, sensei?