The ELK Stack is made of three open-source products: 1) Elasticsearch, 2) Logstash, and 3) Kibana.
Elasticsearch: It is a NoSQL database which is based on the open-source search engine called Lucene.
Logstash: It is a data processing pipeline tool which accepts inputs from sources, performs different transformations, and exports the data to targets.
Kibana: Kibana helps users to visualize data with graphs and chart in Elasticsearch.
https://www.javainuse.com/spring/springboot-microservice-elk