Even though the social structure of Pompeii and Herculaneum was clearly defined, social mobility was possible and many people took advantage of it. The lowest level of society were the slaves. They were mainly foreigners although some Romans sold themselves into slavery to pay off a debt. Both men and women could be slaves and as a slave were the property of their master who was free to do whatever he wanted with them. As such any children born to a slave woman were considered to be the property of the master.
The freedmen (liberatus) and freed women (liberta) were former slaves who had gained freedom either as a gift from their master through a process called manumission or by saving up money to buy their freedom. Once freed many slaves retained a client-patron relationship with their former master. Most worked in some kind of trade and some became extremely wealthy. Some freedmen became citizens however they could never have all the rights of a freeborn citizen.
The highest class of society were the freeborn however the men had greater power than the women. However some women such as Eumachia, Mamia and Julia Felix, were extremely wealthy and played a more active role in society. The freeborn were divided into the plebs humilus (the lowest freeborn), the plebs media (the rich) and the elite (landowning).