"Very well. Here goes nothing. One strength of fire is that it is very powerful. It also is strong against wind, and that is because it feeds the flames and makes them stronger. One of the downsides are, it is hard to tame. That being said, if you play with fire, you're gonna get burned... Unless you can tame it. Then, if tamed, you can use it to burn your victims. I have noticed that most fire techniques are spewed from the mouth, so much be built up in your stomach and lungs. It is also weak against water. Water is fire's natural enemy, and smothers it. Some of the fire style users are Sasuke Uchiha, Itachi Uchiha, Mei, Hiruzen, Madara Uchiha, and Obito Uchiha.
Katon is part of the following KG- Lava Release and Boil Release. It also has a superior form that is known as Blaze Release which is used through Amaterasu, a technique used by some of the few Mangekyou Sharingan users of the Uchiha Clan.
The land that specializes in Katon is the Land of Fire, where the village hidden in the leaves happens to be.
Some jutsu's are Great Fireball, Phoenix Sage Fire, Dragon Fire, and Great Dragon Fire. How was that, sensei?"