[Welcome! If you enjoy worldbuilding, check out my handbook for authors and game designers, Beyond Kings and Princesses: Governments for Worldbuilders.]
Capitalist economies (not the same thing as free-market economies, necessarily) depend on those with money providing capital to firms that need it. For most of human history, most actual investment was done by a small number of people, those with the skills and inclination to form relationships with businesses. Vast amounts of money was economically sterile, being hoarded as gold or silver treasures in the vault of some nobleman or other (just as today one might stuff hundred-dollar bills into a mattress). For the economy to grow and develop, somehow a mechanism needed to be set up to allow savings to be automatically channeled into investment.
This mechanism was the banks. When you deposit money in a bank account, the bank then turns around and lends it to someone who wishes to borrow. The bank serves as an intermediary between you, the saver who wants nothing more than a safe place to store your money (with maybe a little interest on top), and the borrower. Thus, savings that were previously useless to the economy are now being recirculated. (This can lead to systemic fragilities, of course, but those must wait for another post.)
Most bank-dominated systems work in a style called relationship banking. A company forms a long-term exclusive relationship with a bank, that will provide access to capital in exchange for a large degree of control over the company’s decisions—the bank wants to make sure that the company isn’t going to waste the money, after all. This sort of system relies on personal relationships and insider knowledge more than on things like a credit score, which only came into common use in the 1980s or so.
Some economies, such as those in much of Europe, take this logic even further and structure their entire economy around such long-term relationships between firms. Business contracts, decisions on who to hire and how to train them, and access to capital are all made through a close-knit network of powerful executives; insider knowledge and relationships are the key factors here. This is called a coordinated market economy, and you can read a fuller description of it in Hall and Soskice’s Varieties of Capitalism. (Amazon link here.)
Coordinated market economies have some advantages over the American/British system of comparatively liberal market economies. The system in general is more stable; you don’t get the day-to-day disruptions common in the US economy, for example, because everything is based on long-term relationships. In particular, new upstarts find it very difficult to break into such a system, because they can’t get access to capital and they can’t win contracts from existing businesses. While this may seem bad to the American ear, it has the advantage that firms in such an economy can specialize in extremely narrow niches of production, leading to incremental innovation. This is why German companies are known for their precision manufacturing, for example: because they have the luxury of intense specialization in their particular areas.
On the other hand, because it is so difficult for new firms to compete, a continuing hazard of such economies is that the whole system begins to stagnate. Disruptive innovations find it hard to survive in such systems, and instead gravitate to the more open liberal market economies like the United States.
In a liberal market economy, access to capital for big firms is usually gained via the public markets: the stock market and bond market. This means that the long-term relationships typical of Continental economies are less important here. Instead, decisions about who to invest in are driven by the release of public data, for example in annual reports or tax filings. Using such data, market participants decide who to channel their capital to.
There are drawbacks to this system. Particularly in the last thirty years, company executives can be driven to chase quarterly targets at the expense of long-term viability. The business environment is volatile and always changing, making it extremely difficult to plot long-term strategy and to pursue incremental improvement.
On the other hand, this system is much more hospitable to disruptive innovation, as we can see just in the last decade or two. While it can be gut-wrenching while you’re in the middle of it, overall it leads to a more dynamic and healthy economic system over time; stagnation is less of a threat here.
The main difference between these two systems is in the ability to get investment capital without sucking up to a bank. From that relatively minor difference, massive differences in total economic structure can develop. (More details in the Hall/Soskice link.)
Again, institutions matter. And seemingly small differences in institutions can lead to major differences in outcomes.