A pipeline trigger defines when to automatically run a pipeline. There are many types of triggers available: Jenkins jobs, webhooks, CRON jobs, and even other pipelines. Adding a trigger to your pipeline means that the pipeline runs each time the triggering event occurs.
Note: Whether or not you have set up a pipeline trigger, you can always run your pipeline manually.
For more information about how to configure specific types of triggers, see the rest of the pipeline triggers documentation: