Guilds

A guild /ɡɪld/ is an association of artisans or merchants who control the practice of their craft in a particular town. The earliest types of guild were formed as confraternities of tradesmen. They were organized in a manner something between a professional association, trade union, a cartel, and a secret society. They often depended on grants of letters patent by a monarch or other authority to enforce the flow of trade to their self-employed members, and to retain ownership of tools and the supply of materials. A lasting legacy of traditional guilds are the constructed and used as meeting places.

An important result of the guild framework was the emergence of universities at Bologna (established in 1088), Oxford (at least since 1096) and Paris (c. 1150); they originated as guilds of students as at Bologna, or of masters as at Paris.

In medieval cities, craftsmen tended to form associations based on their trades, confraternities of textile workers, masons, carpenters, carvers, glass workers, each of whom controlled secrets of traditionally imparted technology, the "arts" or "mysteries" of their crafts. Usually the founders were free independent master craftsmen who hired apprentices.

There were several types of guilds, including the two main categories of merchant guilds and craft guilds but also the frith guild and religious guild.

...
Wikipedia