At one hand we have the serial, where the story is actually in volumes and flows continuously throughout. Yes, they expect neat cliff-hangers and even conclusions to volumes. But fundamentally, the unit is the whole multi-volume story.
And then we have the independent stories for the character with continuing subplot arcs and supporting characters and the way events from one story are reflected in the next and foreshadowing and call backs ripple forward and back.
Then you have the stand-alones where the characters repeat but there's no connectivity between them. In extreme cases, characters shift from major to minor. Or even to cameos.
Then you get the setting, where nothing is in common but the setting. The stories can be ages and galaxies apart, without so much as mentioning the other stories. (Possibly with subseries of the other type.)
Of course, there is the problem that none of these types are distinct. And that even the borderline cases are not, like the duckbill platypus, securely installed in the borderline. A story with arching subplots often loses the pretext it's a set of different stories and starts to flow from volume to volume. Standalone stories for two or three volumes may start to call back in volume four. And you can have crossovers between books in a setting. . . .
Life is full of complications.