Government and Administration of the Roman Republic
There was no written constitution. The Republic evolved from the struggle between the Senate and the People - Senatus Populusque Romanus - SPQR.
The Senate was the governing body, largely in the hands of the patricians. It prepared proposals to bring before the people, passed decrees (senatus consulta), dealt with emergencies, controlled finances and building contracts, appointed magistrates to provinces, directed foreign relations, and supervised state religion.
The resolutions of the people could have the force of law, but the Senate was allowed greater control. There were four assembles: formal duties, elected magistrates, elected lesser magistrates, passed plebiscite (Latin: comitia curiata, comitia centuriata, comitia tribute, comitia plebis).
A third class emerged (originally from Rome’s cavalry) to engage in trade and finance. These businessmen acquired more political influence and became wealthy. By the time of Cicero, equestrians (also known as equites or knights) could enter the Senate. Cicero tried to reconcile the three classes (senators, equites and plebs) by his concordia ordinum (harmony of the classes).
A magistrate was an official elected annually by the people. Offices were held in a strict order - cursus honorum. After ten years of military service, a young Roman man could begin on the lowest rung of the ladder as follows:
Quaestor - administered finance and maintained public records
Aedile - maintained roads, water supply, and organised games and festivals
Praetor - civil judge, could introduce laws
Consul - commanded army, conducted elections, presided over Senate, carried out decrees
Other magistrates include:
Tribune - defended rights of the common people and had right of veto
Censor - conducted census every five years, conducted purification, revised roll of senators
Dictator - ruled in crisis (maximum of 6 months) and conducted military and domestic matters
Imperium (supreme power) was held by consuls, praetors and dictators
Potestas (power to enforce laws) was held by all magistrates
Information sourced from one of my textbooks