Cloaking is serving a search engine or AI crawler different content from what a person sees. It ranges from the deliberate, showing a bot a keyword stuffed page and a human a clean one, to the accidental, a firewall rule that serves a bot an error while a browser gets the page.
Engines treat cloaking as deception because it breaks the deal: the answer they index and repeat should be the answer a person finds. It risks a manual penalty, and it undermines trust, which for AI answers is everything.
Hidden text is a relative: white text on a white background, text set to font-size zero or text pushed off screen with a negative position. The intent is to feed keywords to a crawler that a person cannot see.
Kenovar's see-as-bot fetches the page as a non rendering AI crawler and as a browser and shows the two side by side, so any gap is visible and it flags hidden-text tricks in the markup. If a bot and a browser disagree, that is the thing to look at.