A storyworld is a literary term refering to a fictional world in which various narratives take place. Storyworlds do not have to be fictional planets, but may be any world where the events of the story take place.
In the contexts of this wiki, the storyworld is, well, exactly that. However, when the term "storyworld" is used here, it is specifically refering to the Course Books storyworld.
You can get a good overview by starting with the Timeline.
While it's a bit tricky to quantify (what with the magic, and all), the Course Books storyworld scores about a 4.5 on the Mohs Scale of Science Fiction Hardness. By and large, it attempts to conform to the actual laws of physics, and the author frequently carries out exhaustive research. Often times the figures you see in the story are real numbers, carefully calculated after assumed values.
Further, the story attempts to maintain internal consistency: once a "rule" is created, it is followed. Attempts are made to base technology on real or at least potentially viable systems, to that end, making the world a work of speculative fiction.
The presence of "magic" complicates matters somewhat, until you dig very deep into the series. In the Course Books, the magic is, itself, technological in nature, with a gene allowing humans to use magic artificially introduced into the population before the Age of Darkness. Magic further has an extensive set of rules, so on the whole it does not detract much.
However, fans of hard sci-fi who hate fantasy are probably not going to appreciate the series.