The Related Links content type can be useful to provide supplemental links that are not part of your site's standard navigation. Probably not something you'll want to include on every page in your site (links such as those should be in your main navigation menu), but there may be cases where you'd like to include links that relate to your page content.
For example, if you have a course listing page, you may want to provide links to the class schedule, academic calendar, and Registrar's office web sites.
The design of the related links menu is understated, compared with the Button and Site Pointer content types. It's a good choice for "nice to have" but not absolutely essential links.
The Related Links content is always positioned in the Right Sidebar column.