From Wikipedia

Hidden History Of Rome

The Plebs were the general body of Roman citizens (as distinguished from slaves) in Ancient Rome. They were distinct from the higher order of the patricians. A member of the plebs was known as a plebeian (Latin: plebeius). This term is used today to refer to one who is or appears to be of the middle or lower order; however, in Rome plebeians could become quite wealthy and influential.

In Latin the word plebs is a singular collective noun, and its genitive is plebis.

The origin of the separation into orders is unclear, and it is disputed whether the Romans were divided under the early kings into patricians and plebeians, or whether the clientes (or dependents) of the patricians formed a third group. The nineteenth century historian Barthold Georg Niebuhr held that plebeians began to appear at Rome during the reign of Ancus Marcius, possibly foreigners settling in Rome as naturalized citizens. In any case, at the outset of the Roman Republic, plebeians were excluded from magistracies and religious colleges. Later on, after a general strike by the plebeians, the law of the Twelve Tables was promulgated, and Tabula XI explicitly forbade intermarriage (which was eventually reversed by the Lex Canuleia). However, before the Twelve Tablets plebeians were forbidden to know any laws, but were still punished for breaking them. Despite these inequalities, plebeians still belonged to gentes, served in the army, and could become military tribunes.

Even so, the "Conflict of the Orders" over the political status of the plebeians went on for the first two centuries of the Republic, ending with the formal equality of plebeians and patricians in 287 BC. The plebeians achieved this by developing their own organizations (the concilium plebis), leaders (the tribunes and plebeian aediles). When the plebeians felt the situation had become dire, they would instigate a secessio plebis, a sort of general strike where plebeians would literally leave Rome, leaving the patricians to themselves.