Shared libraries in Jenkins Pipelines are reusable pieces of code that can be organized into functions and classes. These libraries allow you to encapsulate common logic, making it easier to maintain and share across multiple pipelines and projects. Shared library must be inside the vars directory in your github repository Shared library uses groovy syntax and file name ends with .groovy extension.

How to create and use shared library in Jenkins. How to create Shared library

Login to your Jenkins dashboard. Jenkins Installation
Go to Manage Jenkins --> System and search for Global Trusted Pipeline Libraries.

Click on ADD Button,

Name: Shared_Library
Default version: master
Project repository: https://github.com/sameer-014-Devops/Jenkins_Shared_Library.git

How to use it in Jenkins pipeline

Go to your declarative pipeline
Add @Library('Shared_Library') _ at the very first line of your jenkins pipeline.

Note: @Library() _ is the syntax to use shared library.