Sentry is a tool that helps developers monitor their application's behavior and catch runtime errors and crashes in real-time, providing context to help fix issues quickly. It differs from traditional systems monitoring, log management, and APM by focusing on the health of an application rather than just its performance or resource utilization. By providing in-application context and allowing developers to track issues across distributed services, Sentry helps teams understand the root cause of problems and improve overall application reliability. This is particularly important in modern architectures where infrastructure is abstracted and control is distant from developers.