Fire Release is the usage of superheated chakra to create flames and heat-intensive attacks. Its created through channeling Katon chakra to the user's lungs and exhaling the built chakra in various forms. Katon is most commonly used in its fire-based form, but it can also take the shape of a plume of superheated ash or a misty flammable gas. In terms of raw potential, its considered the least versatile element as it excels in offensive capabilities, lacks in supplementary usage and is ill-suited to use as a defensive element. Despite this, Katon is the most ferocious element to contend with due to its sheer raw power. The heat of the element makes it capable of reducing earthen structures to molten mud, the parasitic nature of it means it preys on the oxygen within wind-based attacks to supplement the flames and even against its elemental superior, large-scale Katon techniques are capable of reducing large bodies of water to scorching mist of dense steam. The Katon element has little usage outside of destruction, to a certain degree its the hardest elemental nature to tame due to its sporadic and uncontrollable nature.
Chakra is a form of life energy that all living individuals produce to some degree and require to survive. Produced within something called chakra coils that mainly surround and connect to each organ that produces chakra, the energy circulates throughout the body in a network called the Chakra Pathway System, which is similar to the cardiovascular system in yer body. Shinobi have learned to generate more chakra and release it outside their bodies through pressure points called tenketsu in order to perform jutsu. Chakra is not normally visible to the human eye, though it can be seen in situations where a person releases as much of their chakra as possible. So as you can see, chakra can be visible like the Rasengan Wind release technique.
Fire is strong against the Wind release element because the air would basically feed the flames, making it become a stronger fire and bigger at that. Although, it can be used in conjunction with Wind release to increase the flames and sometimes it can be strong enough to overpower even the water element. Sometimes fire can also be used with earth and lightning if done correctly. Next, fire is weak against water because it would simply put out the flames because it 'steals' heat from the fire when evaporating, and thus lowers the temperature, making it more difficult (or impossible) for the fire to burn. Also, fire and earth would harden mud earth techniques.
Naturally talented, aren't I?