Pokémon of this type are specialists melee attacks, such as punches and kicks. It could be said they're the opposite to Psychic-type Pokémon because these depend on Special attacks, while the ones of the Fighting type depend on Physical attacks.
Most Fighting-type Pokémon have a human-like body shape, this is because of martial arts and so are mostly practiced by humans.
Fighting-type Pokémon have varied ways to evolve, this is because it represents a fighter going on a journey to get stronger and find who he/she is supposed to be.
They're weak against the Psychic type because of the saying "Mind always beats strength".
They're weak against the Flying type because it's difficult to hit something that's moving in the air.
They're strong against the Dark type because it is famous that goodness always wins, and a fighter must be prepared to face its fears, some represented by the Dark type.
The Poison type resists them because the body is fighter's weapon, and it can be damaged by poison.
The Bug type resists them because some bugs can resist punches easily, also, it is difficult to hit an insect because it's small and moving quickly.
They're strong against the Ice, Rock and Steel types 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 strong against the Normal type because a fighter can easily beat a normal person.
The Ghost type is immune to them because it's impossible to hit an incorporeal being.
They're weak against the Fairy type because physical strength can't do anything against magic.