Patron-client relationship

Patronage (clientela) was the distinctive relationship in ancient Roman society between the patronus (plural patroni, "patron") and their cliens (plural clientes, "client"). The relationship was hierarchical, but obligations were mutual. The patronus was the protector, sponsor, and benefactor of the client; the technical term for this protection was patrocinium. Although typically the client was of inferior social class, a patron and client might even hold the same social rank, but the former would possess greater wealth, power, or prestige that enabled them to help or do favors for the client. From the emperor at the top to the local municipal person at the bottom, the bonds between these groups found formal expression in legal definition of patrons' responsibilities to clients.

Benefits a patron might confer include legal representation in court, loans of money, influencing business deals or marriages, and supporting a client's candidacy for political office or a priesthood. In return, the clients were expected to offer their services to their patron as needed. A freedman became the client of his former master. A patronage relationship might also exist between a general and his soldiers, a founder and colonists, and a conqueror and a dependent foreign community.

One of the major spheres of activity within patron-client relations was the law courts, but clientela was not itself a legal contract, though it was supported by law from earliest times. The pressures to uphold one's obligations were primarily moral, founded on the mos maiorum, "ancestral custom" ,and the qualities of fides ("trust, reliability") on the part of the patron and the pietas ("dutiful devotion") demonstrated by the client. The patronage relationship was not a discrete unit, but a network, as a patronus might themselves be obligated to someone of higher status or greater power, and a cliens might have more than one patron, whose interests could come into conflict. While the Roman familia ("family", but more broadly the "household") was the building block of society, interlocking networks of patronage created highly complex social bonds.

...
Wikipedia