Third-party data refers to information collected and shared by external sources, rather than directly from the individual or organization it pertains to. This data is often obtained through partnerships, purchases, or other agreements between companies, and can include demographic, behavioral, and interest data. It is used by businesses and marketers to gain insights into their target audience and inform their strategies and decision-making. However, concerns about privacy and accuracy have led to increased regulations and scrutiny surrounding the use of third-party data.