The guy in the middle is the original, the guy on his left is his clone (Although that particular picture is the clone with the original's face) and the one on the right is a guy who was brainwashed to think he was the guy in the middle and had surgery to look like him.
The first is Solid Snake, one of three clones of Big Boss.
The second is Big Boss, a legendary soldier and terrorist who was cloned.
The third is Punished "Venom" Snake, or as I liked to call him Venom "Punished" Snake, or as I liked to call him Ahab, or as I liked to call him Medic. He was a non-genetic clone of Big Boss who got a piece of shrapnel the size of a football lodged in his head somehow and was hypnotized in a coma into thinking he was Big Boss. And he was a good friend.