Whenever we play games that take place in a medieval setting, its a given that there are "shops" around, buildings that you can into to buy all sorts of things, from books to potions. They aren't quite supermarkets, but look a lot like the corner markets from a century ago.
How realistic would it have been to have such a shop in let's say Europe in the middle ages? Would merchants sell their wares on markets exclusively? Would there be buildings in which a shopkeeper would just sit all day waiting for people to enter and buy things? Would it be more common to commissoin something like let's say a book or a set of cups or plates instead of buying some that someone had in stock?
You'll see it pointed out here that medieval covers about 1,000 years. So, it's a bit much to generalize. But you can see a late medieval shop in Jost Amman and Hans Sach's 16th c. Book of Trades (Das Staendebuch). Here's a shoemaker. Here's a tailor. Here's a blacksmith. Here is an illuminator. There may be some artistic license employed in making these seem very similar. But there would be some expected similarities. A shop would need light- craftspeople need to see what they are doing. In this period, that would be daylight, so windows are needed. Those can have glass in them- like the Illuminator- but that is an expensive thing perhaps. So, instead there might just be an open window. And, that could serve as a counter, as well: as you can see with the shoemaker, the customers are on one side, the shoemaker on the other. There would then be shutters to close up the window- and close and secure the shop. Of course, the tailor would not limit customers to the counter: they had to be measured, fitted. But security would be a concern. Things were expensive, in the pre-industrial world, and goods simply lying out on shelves for examination in the modern way would have been very risky.
There would also be periodic markets, of course. A village market might have the very simplest of arrangements, like Jan Brueghel the Elder's farmers here selling out of baskets, off wagons. But you could easily imagine something temporary in the way of a stall. Here for example you can see to the left and right ( Portugal, early 16th c.) a couple of stalls have been set up with awnings to protect from sun or rain. They take advantage of the wall of the Church- it provides support for their stalls. But it also adds some security- the stallholders don't have to be watching that merchandise doesn't get swiped behind their backs.
There would tend to be a concentration of crafts in the later middle ages. For metalwork, there was Nuremberg, and for books, there was Frankfurt. And so there was a yearly book market in Frankfurt, and you can see in the Frankfurt Buchmesse of the late 17th c. here far more of those stalls set up- it's not hard to imagine something similar in the 15th c.. Note that almost 200 years later they also take advantage of a wall, just like the 16th c. ones in Portugal.
There are a variety of links to period images of such markets here
More of Jost Amman's woodcuts of trades here
Not a full answer to your question, but worth a read while waiting for a more specific answer: I'm going shopping in a large medieval European town or city in the Late Middle Ages. What can I buy? written by u/gothwalk
