While the Test Repository addresses the organization of Tests within the scope of a given project during the specification phase, the Test Plan Board does it at the planning level (and as consequence, at execution).
The Test Plan Board gives enables you to organize the Tests that are part of your Test Plan in multiple folders and sub-folders. Implicitly, you can also define the order of the Tests and the relevance of those grouped Tests (i.e., folders) by ranking them within the tree presented within the Board.
By providing you the ability to define groups and sub-groups (i.e., folders and sub-folders) for the Test Plan's Tests, you're able to track them independently and see right away their current status, even if the scope of the Test Plan is broader. You can also more easily do operations for those subsets of Tests, such as creating Test Executions.
