Mars was the second most important god in the roman culture. He was father of Romulus who was the founder of Rome. Which was one reason mars was one of the most important gods of Rome. The other reason is that he was the god of war. War was very important to the Romans because the engage in battle so much obviously they wouldn't want to lose, so they worshiped mars and asked for victory in battle.
Mars was the sun of the supreme god, Jupiter.
In earlier times Mars was the god of agriculture.
Greek counterpart = Aries
Pluto played an important roll in the roman empire and roman republic. He was the keeper of the dead and the guardian of the underworld. The underworld is not the place of pain and torture as we see it today, it was merely the place that you go when you die.
Pluto was important because everyone wanted to be treated fairly when they die, and to the Romans if they worshiped Pluto you would be when you die.
Pluto was awarded everything underground.
Pluto could send gifts into the soil from the underworld.
Greek counterpart = Hades
Jupiter was the most important god in Rome, for he was the supreme god or the god of gods. Jupiter kept the heavens in order, he dealt with the other gods problems and wars, yet he had enough time to deal punishment and death to criminals, and mercy and savior to those who worshiped him. Jupiter was the "boss" of gods, so to make sure prayers were answered the people of Rome would worship him.
Jupiter is the brother of Pluto and the father of Mars.
Jupiter was the symbol of power, rule, and law.