When this is set to "N", all protected links that the viewer/member is not eligible to access "yet", is removed from display (basically links are hidden from view - but content itself will continue to remain protected regardless of whether link shows up in the menu or not).

When Sneak Peek (a different config setting) is set to "Y", all links to all protected content will show up in the menus. BUT... turning on Sneak-Peek also means that ALL protected posts and pages will show the content body up to the WordPress "more" tag. Sometimes, you want to show links in the menu without turning on Sneak-Peek.

And that's exactly when this config item is going to come in handy.

Default: N