Network traffic refers to all network requests made by a browser when loading a web page, including requests for JavaScript, CSS, and image files. Capturing network traffic provides valuable insights into the performance of a web application, allowing developers to identify potential issues before shipping to production. This can include analyzing HTTP status codes, request and response sizes, and resource loading times. By using tools like PhantomJS or BrowserMob Proxy, developers can create scripts to capture network traffic in real-time, enabling them to optimize their web applications for better performance and user experience. These scripts can also help identify issues with caching, rendering speed, and other factors that may impact the end-user experience. By incorporating network monitoring testing into their pipelines, teams can ensure a smoother transition from development to production, reducing the likelihood of errors or performance issues that may affect users.