The glossy pictures you see in magazines and the pop-ups on your phone that promise you’ll be happy, rich, and/or beautiful forever if you just buy this one brand of gum/cola/whatever.
Businesses use advertisements to try to get you to buy stuff. Ads show up on TV, the Internet, and in newspapers. The advertiser only has limited control over who sees the ad, though. It could be you, your grumpy Uncle Dean, or your little sister (who’s too young to care, anyway).