Custom action in text component

Hi there 🙂 As i updated my minigames on 1.21.7, i saw this new tip (screen). I don't really understand what it means (if theses "custom events" are datapacks ones, modded, etc.) or if it could be interesting for my games, could someone give me some examples or complete explanation for this ? Just for information, as i'm non english native, i don't understand the "payload" concept in this case even after traduction