Shinra
The Shinra is a powerful and evil organization that rules the world with money, power & fear. They own a monopoly on electricity. They harnest Mako energy from the Earth to run they're company and to make money.
Mako energy comes from every organic creature. When we die, or spirit energy goes down into the Earth, where all the other spirit energy meet. This is the life streams. It gushes out some ends of the earth, Mideel. Without these life streams running through the Earth, the planet would fall a part & die.
Mako, a source created by compressing spirit energy, can produce power & electricity. When compressed even more it turns into a crystallized form, called materia. This contains knowledge of the spirit energy. When used, the knowledge interfaces with the Earth, and magic is cast.
President Shinra: The creator and founder of Shinra. He rules the world with his money, He will kill innocent people to get few people out of his way.
Vice President Rufus Shinra: He's the son of President Shinra. Rufus is not afraid of death, while he likes to rule the world with fear and power.
Palmer: He's the leader of the Galactic Development. He is pretty old man.
Scarlet: The leader of Weaponary Development. She has one bad attitude.
Heidegger: The leader of Public Welfare & he hires the Turks for himself.
Professor Hojo: The leader of the Chemical Development. He's a crazy & mad scientist. He also is the father of Sephiroth. He joined Shinra, after Proffessor Gast went Missing.
Reeves: The leader of the Municipal Development. Nobody likes him. He is not as evil as the others in some way the complete opposite. He is the one that controls CaitSith.