Pipelines placed in a pattern project show up on the Patterns Catalog tab on the left. When you open a pipeline pattern in Designer, a copy of that pipeline is made for you to configure as needed. This is similar to a template.
A nested pipeline is when you drag an existing pipeline from the Pipeline Catalog onto the canvas so that you don’t have to rebuild the same segment again. For example, say you have multiple pipelines gathering information and they all need to be mapped a certain way and emailed to the same set of people. Rather than configuring a Mapper and Email Sender over and over again, you can create a pipeline with just this snippet and reuse this piece instead. The down side to nested pipelines is that if that pipeline is changed, the other pipelines using it will also be updated, which may not be what you intended.
