Importing a Timeline allows you to work with an editorial sequence that contains shots and soft transitions (such as dissolves). In this case, timelines are created in a Visual Effects and Finishing application and Lustre gains access to the timeline by way of Wiretap. This is a useful workflow for shot-to-shot grading.
Lustre renders the final clip to local storage using one of the four rendering options in the Render Local menu. See Specifying the Destination for Local Render Files.