A Facebook Pixel is a piece of code added to your website that tracks user actions, such as page views, purchases, or sign-ups, after they click on your ads. It’s essential for optimizing Facebook ad campaigns as it helps track conversions, improve ad targeting, and deliver ads to users most likely to take action. The Pixel also enables retargeting, allowing you to re-engage users who didn’t convert, and provides data to build Lookalike Audiences for broader reach. Overall, the Pixel is a vital tool for maximizing the effectiveness and ROI of your Facebook ads.