The document discusses behavioral targeting, which tracks a user's online activity to send relevant content. It describes how cookies store information to identify users and their interests across websites. Behavioral targeting can occur on individual sites, across networks, through retargeting, or using ISP data. While it personalizes the user experience and targets audiences, it also raises implications for user privacy that require solutions like opt-out options and cookie management settings. The use of behavioral targeting in online advertising is growing significantly and expected to continue rising in the future.