What are Elasticsearch plugins?

Plugins are used to extend the basic capabilities of Elasticsearch in a customized way; for example, by adding custom mapping types, custom analyzers, native scripts, custom discovery mechanisms, and more. A plugin must contain a property file, named plugin-descriptor.properties, and it may optionally contain JAR files, scripts, and configuration files. The source of plugins can be classified into two types. The first one is the built-in core plugin that is part of the Elasticsearch package and is maintained by the Elastic team. The second one is developed by individuals or different communities. For example, the ICU Analysis plugin and the Smart Chinese Analysis plugin (for more information about these plugins, refer to https://github.com/elastic/elasticsearch/tree/master/plugins) are the core plugins shipped with the product, while the IK Analysis...