FirstPaint` and `firstContentfulPaint` metrics provide insight into when a user perceives a website as ready to use, but these metrics don't always occur in a consistent time frame. In contrast, interactivity metrics such as `firstInteraction`, `firstInputDelay`, and `longRunningTasksCount` measure how long it takes for a web page to become usable, allowing developers to identify performance issues and optimize their code. These metrics can be used to improve customer experience by correlating perceived performance with business KPIs, eliminating performance issues in pre-production, writing code that utilizes performance budgets, testing code in a lab environment, deploying code with alerts and telemetry data, performing competitive benchmarking, and using real user monitoring in the production environment. By leveraging these metrics, developers can gain a better understanding of their website's performance and make data-driven decisions to optimize their digital customer experience.