3 What's a Jenkins plugin?

Jenkins can be extended via its plugin architecture. A standard Jenkins plugin has a backend implemented in Java and a web UI implemented through the Jelly framework. At present time there are more than 1000 available plugins in the official Jenkins Update Center and it is possible to implement your custom plugins using the powerful Jenkins APIs. If you are interested in implementing a custom plugin you can follow this quick tutorial to start from scratch.
There are different types of plugins for Jenkins. publishtokafka-plugin is a post-build action plugin: this category of plugins can be added to a build job to execute at the end of the core build steps.