Contextual data is information that is relevant to a specific context or situation. In the context of online advertising, contextual data refers to information about the content or theme of a webpage or app that is used to serve relevant ads to users.

Contextual data can be used to help advertisers and marketers target specific audiences or segments by understanding what users are interested in and what they are likely to respond to. For example, if a user is reading an article about travel, an advertiser might use contextual data to serve them ads for travel products or services.

Contextual data can be gathered from a variety of sources, including the words and phrases used on a webpage or app, the images and videos displayed, and other contextual cues. It is often used in combination with other types of data, such as demographic or behavioral data, to provide a more comprehensive understanding of the user.

Contextual data can be used to improve the effectiveness of online advertising campaigns by helping advertisers to reach users with ads that are more relevant and engaging. It can also help advertisers to optimize their targeting and increase the return on investment of their ad campaigns.