Audience extension is a digital advertising technique that allows advertisers to reach a broader audience than they would be able to through their own website or owned channels. This is typically done by partnering with other websites or platforms that have access to a larger or different audience, and placing ads on those sites. For example, an advertiser who sells sports equipment may partner with a sports news website to extend their reach to readers of that site who may be interested in their products. Audience extension can help advertisers to increase the visibility of their ads and drive more traffic and engagement to their website.