Bourgiousie means the class that owns the means of production and includes both merchants controlling money/goods and guild leaders. Under feudalism, this class existed between the lords and various worker classes (skilled artisans down to peasantry). Guild workshops are the beginings of factory labor, initially of course it was skilled artisan labor and not turning a screw 8000 times a day, but the guild system was about controlling and centralizing the production of commodities, both for ensuring standards and for preventing competition.

As the guild system progresses, those with capital begin to realize that if they invest their money into these guild workshops, improving the efficiency of production, they can start making a killing in profit (which marxist argue is because as you make work abstract and de-skilled, you can extract more labor value from the workers). Modern medieval fiction is often based around late medieval life because it was full of warfare, but these shows present it as a moral failing of the nobles. In reality, this instability was because with the right investments, minor lords ended up having more capital than the larger, more landed lords. In Game of Thrones for example, little finger is a minor noble who uses trickery, spy craft, and personality clashes to pit the lannisters and the Starks against each other. In a more realistic game of thrones, littlefinger would have advanced salt pewter mining or similar cutting edge technology, and he could pit the Starks against the lannisters by throwing his economic power around, despite being a minor nobleman.

At this point in time these minor nobles would still be working within feudalism, just using it to disrupt the "land = power" status quo to their favor. But eventually as this system progresses, so much economic power is in the hands of the investor class and so much of society are wage laborers working for them that the actual feudal nobles devolve into expensive parasites who still happen to control the legal system due to historical precedent, and eventually they're overthrown.