Third-party data is data that is collected by an entity or a provider who has no direct connection or relationship with the users. Data from different sources, such as government, non-profit, or academic ones (e.g., weather data, public demographic data), can be combined or exchanged on data marketplaces or platforms. It is used in marketing to run targeted ad campaigns, discover new audiences, or get insights about current users. However, it may not be as accurate or useful as first-party, and it may have issues with compliance and privacy regulations.