Pokémon of this type are specialists in melee attacks, such as punches and kicks. It could be said that they're the opposite to Psychic-type Pokémon because while Pokémon of that type depend primarily on special attacks, Pokémon of the Fighting type depend mostly on physical attacks. In particular, every Fighting-type attack introduced before Generation IV remained a physical attack, with special Fighting attacks only being introduced from Generation IV onwards.
Most Fighting-type Pokémon have a human-like body shape because they represent practitioners of various martial arts, which tend to be real-world humans. Some Fighting-type Pokémon are represented by looking like fighters (Machamp looks like a bodybuilder and Crabrawler looks like a French-wrestler) while other are represented by being based on a certain type of fighting style (Hitmontop is based on capoeira fighting and Gallade is based on sword-fighting). A considerable number of Fighting-type Pokémon are predominantly or exclusively male. They can also be represented by simply just having incredible strength (such Pokémon such as Bewear, Pangoro, Crabominable, Conkeldurr and others have this).
Fighting-type Pokémon have varied ways to evolve as this represents a fighter going on a journey to get stronger and find out who he/she is supposed to be.
They have no effect against the Ghost type because it's impossible to hit an incorporeal being. However, the Fighting type is neutral to the Ghost type.
They're strong against the Dark type because it's a common theme in martial arts and fighting fiction that heroism always wins, and a fighter must be prepared to face his/her fears, some of which are represented by the Dark type.
They're strong against the Normal type because a fighter can easily beat a normal person.
They're strong against the Ice, Rock and Steel types in terms of textures because ice can be shattered with a strong punch, some fighters are trained to destroy rocks, and steel objects can be easily bent.
They're weak against the Psychic type because the brain also regulates all muscle functions in most animals, and the most skilled master minds can overpower the most skilled fighters, hence the term "brains over brawn" and "mind over matter".
They're weak against the Flying type because it's been long said that height is a large advantage when it comes to battle, as it's difficult to hit something that's moving in the air and that dropping attacks have the advantage of gravitational acceleration when it comes to attacking. It may also be due to the fact that doves are symbols of peace.
They're weak against the Fairy type because physical strength can't do anything against magic, especially when the welders of magic can put a spell on them.
They resist the Bug type because fighters, with their strength, can easily withstand bugs.
The Bug type resists them because bugs generally have an exoskeleton which can protect them from blows. This is also evident as these Pokémon of that type are much bigger than average insects.
The Poison type resists them because the body is a fighter's weapon, and it can be damaged by poison. Interestingly, they're not weak to the Poison-type.