IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.
Transforms enable you to convert existing Elasticsearch indices into summarized indices, which provide opportunities for new insights and analytics. For example, you can use transforms to pivot your data into entity-centric indices that summarize the behavior of users or sessions or other entities in your data. Or you can use transforms to find the latest document among all the documents that have a certain unique key.
Intro to Kibana
ELK for Logs & Metrics