Monitoring Python applications is crucial to ensure optimal performance and identify bottlenecks quickly. There are four layers to consider: presentation layer (user interface), business layer (application logic), persistence/database layer (database interaction), and metrics collection (data analysis). Monitoring tools can provide insights into response time, throughput, error rate, CPU usage, memory usage, Apdex score, and other key metrics. Distributed tracing allows tracking requests through the system to identify issues in complex applications. Open-source tools like OpenTelemetry, Prometheus, Jaeger, Zipkin, logging, and structlog are available for monitoring Python applications. However, using a consolidated platform like New Relic can simplify monitoring by including automatic instrumentation, built-in visualizations, real user monitoring, synthetic monitoring, distributed tracing, and more.