Versioning of Pipelines enables you to create different versions of the same pipeline and rollback to a previous version for testing purpose.
When you create a new pipeline, initial version is 1 by default. Once you update the pipeline, you can either create a new version or overwrite changes in the exiting version.
Note: If you create a new version of the pipeline, update the comment (not mandatory but required to keep track of the changes).
If you want to switch the version of a pipeline, click on the option on the pipeline canvas to switch version, as shown below:
This brings the window shown below, where you can choose the versions.