Hi@Anil,
GitHub webhook is used to trigger jenkins job automatically. For an example, say you have local git repo in your system. And create one pipeline with GitHub and jenkins.
Now whenever you upload something in GitHub, webhook will automatically trigger your jenkins job and jenkins will download the files in workspace.
But one thing you have to take care that GitHub has public IP. To create web hook for jenkins, you need Public IP of jenkins.
Hope this will help.