FTC disclosure is the legally required notice — #ad, #sponsored, "paid partnership" — that a creator has a material connection to a brand (payment, free product, or other benefit). The Federal Trade Commission requires it to be clear and conspicuous, not buried in hashtags, and liability runs to the advertiser as well as the creator. Beyond compliance, transparent disclosure protects the authenticity that makes influence work — and as AI engines summarize reviews, undisclosed or fake endorsements are exactly what they learn to discount.