Explanation:
It all began when the Romans overthrew their Etruscan conquerors in 509 B.C.E. Centered north of Rome, the Etruscans had ruled over the Romans for hundreds of years.
Once free, the Romans established a republic, a government in which citizens elected representatives to rule on their behalf. A republic is quite different from a democracy, in which every citizen is expected to play an active role in governing the state.
The Roman concept of the citizen evolved during the Roman Republic and changed significantly during the later Roman Empire. After the Romans freed themselves from the Etruscans, they established a republic, and all males over 15 who were descended from the original tribes of Rome became citizens. Citizens of Rome distinguished themselves from slaves and other noncitizens by wearing a toga; most wore a white toga. During the Empire, each emperor wore a purple toga to distinguish himself as the princeps, or "first citizen."
Citizenship varied greatly. The full citizen could vote, marry freeborn persons, and practice commerce. Some citizens were not allowed to vote or hold public office, but maintained the other rights. A third type of citizen could vote and practive commerce, but could not hold office or marry freeborn women.
In the late Republic, male slaves who were granted their freedom could become full citizens. Around 90 B.C.E., non-Roman allies of the Republic gained the rights of citizenship, and by 212 C.E, under the Edict of Caracalla, all free people of the Roman Empire could become citizens.
Frescoes line the walls of long-forgotten Etruscan tombs. This painting, found in the Tomb of Augurs in Tarquinia, is titled Hell's Door.
The aristocracy (wealthy class) dominated the early Roman Republic. In Roman society, the aristocrats were known as patricians. The highest positions in the government were held by two consuls, or leaders, who ruled the Roman Republic. A senate composed of patricians elected these consuls. At this time, lower-class citizens, or plebeians, had virtually no say in the government. Both men and women were citizens in the Roman Republic, but only men could vote.
Tradition dictated that patricians and plebeians should be strictly separated; marriage between the two classes was even prohibited. Over time, the plebeians elected their own representatives, called tribunes, who gained the power to veto measures passed by the senate.
Gradually, the plebeians obtained even more power and eventually could hold the position of consul. Despite these changes, though, the patricians were still able to use their wealth to buy control and influence over elected leaders.

Hannibal marched his elephants south into the Italian peninsula during the Second Punic War.
The Roman Senate
The history of the Roman Senate goes as far back as the history of Rome itself. It was first created as a 100-member advisory group for the Roman kings. Later kings expanded the group to 300 members. When the kings were expelled from Rome and the Republic was formed, the Senate became the most powerful governing body. Instead of advising the head of state, it elected the chief executives, called consuls.
Senators were, for centuries, strictly from the patrician class. They practiced the skills of rhetoric and oratory to persuade other members of the ruling body. The Senate convened and passed laws in the curia, a large building on the grounds of the Roman Forum. Much later, Julius Caesar built a larger curia for an expanded Senate.
By the 3rd century B.C.E., Rome had conquered vast territories, and the powerful senators sent armies, negotiated terms of treaties, and had total control over the financial matters of the Republic.
Senatorial control was eventually challenged by Dictator Sulla around 82 B.C.E. Sulla had hundreds of senators murdered, increased the Senate's membership to 600, and installed many nonpatricians as senators. Julius Caesar raised the number to 900 (it was reduced after his assassination). After the creation of the Roman Empire in 27 B.C.E., the Senate became weakened under strong emperors who often forcefully coerced this ruling body. Although it survived until the fall of Rome, the Roman Senate had become merely a ceremonial body of wealthy, intelligent men with no power to rule.
Occasionally, an emergency situation (such as a war) arose that required the decisive leadership of one individual. Under these circumstances, the Senate and the consuls could appoint a temporary dictator to rule for a limited time until the crisis was resolved.