An advertisement (often shortened to ad) is a public message designed to persuade people to buy something, do something, or think something. Advertisements appear everywhere: on billboards along highways, during commercial breaks on television, in magazines, on websites, and even on the sides of buses.

Companies create advertisements to convince you that their product is worth buying. A cereal company might run an ad showing happy kids eating breakfast, hoping you'll ask your parents to buy that brand. A movie studio creates advertisements showing the most exciting scenes to get people into theaters. Political candidates run advertisements to persuade voters to support them.

The word comes from the Latin advertere, meaning “to turn toward,” which makes sense: advertisements try to turn your attention toward whatever they're promoting. While some advertisements simply provide information (like a “Help Wanted” sign in a store window), most use persuasive techniques, such as catchy music, funny jokes, celebrity endorsements, or appeals to your emotions.

Learning to recognize advertising helps you think critically about the messages around you. When you see an ad claiming a toy is “the most amazing ever,” you can ask yourself: Is this informative, or is someone just trying to sell me something? Understanding advertisements means understanding when someone is trying to influence your choices.