When you have multiple Pipeline jobs, you often want to share some parts of the Pipeline scripts between them to keep Pipeline scripts DRY. A very common use case is that you have many projects that are built in the similar way.
This plugin adds that functionality by allowing you to create “shared library script” SCM repositories. It can be used in two modes: a legacy mode in which there is a single Git repository hosted by Jenkins itself, to which you may push changes; and a more general mode in which you may define libraries hosted by any SCM in a location of your choice.
Comprehensive user documentation can be found in the Pipeline chapter of the User Handbook.