Any way to introduce us to these concepts?
I’d say that cultivation stories are about as big as isekai.
Dragon Ball is very much Xianxia-ish. Softcore Xianxia, so to speak. On the other end, much of Hindu mythology can be seen as an inspiration for what later became xianxia.
Hard training, eating enormous quantities of powerful food or medicine, meditating and fighting eventually lead to you gaining a level and transforming into the next stage. Like Dragon Ball, it often starts as a martial arts story, then they learn to fly and shoot energy/elemental attacks from their hands. Later on, destroying mountains or (eventually) even planets, or ascending to a higher plane of existence are very much possibilities.
Details on how this works differ. Some have game-like mechanics (Gather exp/energy → level up). Some require meditation on the nature of yourself and/or the world to increase their cultivation realm. Dragon Ball requires you to scream a lot during a fight… Many require specific actions to "break through" to the next level, sometimes involving a trial of some sort.
Ryuugi over at spacebattles.com has written a bunch of high-effort posts detailing the historical and mythological background, as well as explaining basic concepts in far too much detail. His stories are very much inspired by mythology and classical texts, so it may nor be a perfect representation of modern cultivation. Less so, because he writes crossover fanfiction as a western author, but I can recommend checking it out anyway.
Here are the informational threadmarks for a Xianxia/Worm story called "Sect":
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Here’s the same for a Xianxia/Sailor Moon crossover:
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On second thought, those links are probably more interesting after you already know xianxia.
This glossary is probably more useful to get basic information:
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