These came to be popular in mid 80s, and gradually became more popular than other kinds of bars. They also became more like them, the main distinction being the music they play, how loud, and the choice of coffee and drinks. They usually prefer to sell 0,33l beer and less that of 0,5 or on tap (of which they have maybe one kind), nes or espresso vs turkish coffee, and generally won't have a špricer.
What they usually do have is tables on the sidewalk - be it a sufficiently wide regular sidewalk, or space in some of the pedestrian zones, which most of the cities have. Sometimes, in streets with fewer pedestrians, they simply take over the sidewalk and expect anyone to just walk through, between the tables.
They come in all sizes, and specially shapes.
Sometimes they are a combination of a cakeshop, pizzeria, a betting joint, a bar - any two or three of these. They almost never have a prominent barbecue, as a traditional kafana would have.