We tend to think of labor and management as two separate groups, groups that indeed are comparable from one locality to another. That is why modern labor unions are national or even international. But medieval guilds were different.
As cities grew in the twelfth century, a major component was the guilds, associations of artisans that all made the same sort of thing. A guild included everyone from the masters down to the boys starting their apprenticeships, so labor and management were not considered separate categories. There was no sense of solidarity between guilds making the same product in different cities; any member of the shoemakers' guild in one city would have told you that the shoemakers' guild in the next city over was well known for its shoddy products and high prices.
Although each guild set its own requirements, there were many similarities. To become a member of a guild, one usually started young, around six or eight, the same age as a boy might be when sent off to the church or to begin his knighthood training. One began as an apprentice, doing simple, low-level tasks in a shop, like sweeping up or carrying messages. It helped to be from a guild family; some guilds were wary of letting in "outsiders." Parents placing a boy in a shop as an apprentice had to pay a sizable fee, because the boy would have to be fed, housed, and clothed for years before he became an economic asset.
An apprentice advanced from simple tasks to slowly learning the trade. At this point he would become a journeyman, someone who knew what he was doing and would be paid to do it. (The word, by the way, doesn't mean someone taking a trip but rather someone paid by the day, journée in Old French.) A journeyman typically moved out of the shop where he'd lived since boyhood, even if he still worked there.
Journeymen were hired by the masters, those who actually ran the shops. All journeymen must have dreamed of becoming masters, but only a few could. They would need enough capital to buy a shop--again, being from the right family helped a lot--and especially needed to produce a "masterpiece," something to prove to the other guild masters that they had become so good at their craft that they were qualified to join them.
The shops combined retail and work space on the street level. Large, arched doors stood open except in the worst weather, letting in both light and customers. The upper floors were where the master's family and the apprentices lived, somewhat above the noise and smells of the street.
Different shops in a guild would coordinate with each other and usually all be situated on the same street; they might even claim the local parish church as their church. The messier guilds, like the leather tanners (who produced a lot of waste hair and flesh as well as unpleasant chemicals) would be on the downstream side of town. Guilds regulated both quality and prices, so as not to undercut each other. People shopping for a particular product would choose one shop over another for its features or personal service.
Guilds included everything from shoemakers to jewelry makers to masons to prostitutes. The professors of a university belonged to the professors' union (universitas is indeed medieval Latin for what we'd call a guild). Although most guilds were run by men, a few, like the ribbon-maker's guild, were all female. Women might also become masters if they were the daughter or widow of a master and could prove they knew the craft.
For more on medieval city life, see the following post.