This document provides an overview of the ELK (Elasticsearch, Logstash, Kibana) stack for collecting, analyzing, and visualizing log and metrics data. It describes the components of the ELK stack and how they work together, including how Logstash can be used to transform raw log data into structured JSON documents for indexing in Elasticsearch. The document also discusses how Kibana can be used to visualize and explore the data in Elasticsearch, and how the ELK stack can be used for advanced capabilities like custom metrics, alerts, and monitoring through tools like Elastalert and Kibana dashboards.