Advertising law asks one deceptively simple question: what did the ad actually communicate to a reasonable consumer, and could the advertiser prove it before running the ad. This article explains the deception and unfairness standards, the substantiation requirement that exists nowhere in the statute yet decides most cases, and the line between puffery and a factual claim. It covers endorsements and influencer disclosure, comparative advertising, pricing and discount claims, environmental and origin claims, and the design practices regulators now treat as deceptive. It explains the four enforcement tracks — FTC, state attorneys general, competitors under the Lanham Act, and the self-regulatory NAD process — and why competitors are often the fastest threat. Examples run through a fictional skincare brand to show how ordinary marketing copy becomes a legal claim. Readers finish able to review an ad the way a regulator would.