On the Elasticsearch website, we can find the following description:

Index templates allow you to define templates that will automatically be applied when new indices are created. The templates include settings, mappings and a simple pattern template that controls whether the template should be applied to the new index.

https://elastic.co

Elasticsearch doesn’t know the desired structure and format for our data. It receives a lot of alerts and tries to parse them, that’s all. If no template is available, it creates an index using what it thinks is correct, […]