A tracking pixel is a small, transparent image, usually just 1x1 pixel in size, embedded in web pages or emails. It is used to collect data about user interactions, such as page views or email opens. When a user visits a page or opens an email containing a tracking pixel, it sends information back to the server, helping marketers understand user behavior. These pixels are often part of digital marketing strategies, allowing businesses to measure the effectiveness of their campaigns. By analyzing the data gathered from tracking pixels, companies can optimize their content and improve user engagement, ultimately enhancing their overall marketing efforts.