The document discusses the ELK stack which includes Elasticsearch, Logstash, and Kibana. It describes the workflow of using Logstash to parse and filter logs, Elasticsearch to index the data, and Kibana to visualize the indexed data. It provides examples of how the ELK stack can be used for log parsing, real-time metrics monitoring, and anomaly detection. The document also mentions options for running the ELK stack in the cloud or as a hosted service.