An ad is short for advertisement, which is a public notice designed to inform people about something or persuade them to buy, support, or do something. You see ads everywhere: on websites, in magazines, during TV shows, on billboards along highways, and even before YouTube videos.

Ads come in many forms. A commercial for a new video game is an ad. A poster announcing tryouts for the school play is an ad. When a company wants people to know about its product, it creates ads to spread the message. Political candidates run ads to convince voters to support them. Charities create ads to raise awareness about important causes.

In everyday conversation, when someone says “I saw an ad,” they're almost always talking about an advertisement.

Good ads grab your attention and stick in your memory. Some are funny, some are emotional, and some simply give you useful information. Learning to recognize what ads are trying to accomplish helps you make smarter decisions about what messages to trust and what to question.