Application Performance Monitoring (APM) is a crucial component of observability, working alongside logs and infrastructure metrics to provide comprehensive insights into application performance. Logs record events and are human-readable, while metrics provide periodic summaries, both focusing on infrastructure rather than application specifics. APM bridges these gaps by focusing on the application layer, enabling developers to monitor end-user experiences and identify bottlenecks and errors. Elastic APM, integrated into the Elastic Stack, offers a curated user interface with visualizations and dashboards, allowing users to track transactions, traces, and exceptions. It provides detailed context about application performance, helping prioritize fixes and optimize performance. Elastic APM is open-source and integrates with Elasticsearch, allowing users to deploy it easily via Elastic Cloud or locally, and it supports various licensing levels for additional features like alerting and machine learning.