When module baselines are created in a baseline set, links between objects are copied into the baseline set. Copying the links with the baselines means that when you follow a link between modules in the baseline set, the link goes to the baseline, not to the current version of the module. You can see what links existed, and the data that was linked at the time the baseline set was closed.
Links to and from module baselines that are not part of a baseline set can only be followed from the baseline to the current version. There is no corresponding link from the current version to the baseline of the linked module.