Advertisers bid on keywords that users of services such as Google and Bing might enter when looking for certain products or services, which gives the advertiser the opportunity for their ads to appear alongside results for those search queries.

These ads, often known by the term pay-per-click ads, come in a variety of formats. Some are small, text-based ads, whereas others, such as product listing ads (PLAs, also known as Shopping ads) are more visual, product-based advertisements that allow consumers to see important information at-a-glance, such as price and reviews.