This document introduces the ELK stack, which consists of Elasticsearch, Logstash, and Kibana. It provides instructions on setting up each component and using them together. Elasticsearch is a search engine that stores and searches data in JSON format. Logstash is an agent that collects logs from various sources, applies filters, and outputs to Elasticsearch. Kibana visualizes and explores the logs stored in Elasticsearch. The document demonstrates setting up each component and running a proof of concept to analyze sample log data.