What it means
A shared link is a URL that grants the access allowed by its link settings to whoever meets those conditions. A shared-folder member is an account added directly to collaborate or view within the folder. The same person can have both paths. Changing one path does not necessarily close the other, and team or parent-folder membership may add a third path.
A real-world example
A contractor is removed from a project folder but keeps a bookmarked view link. If the link remains active and permits that audience, the contractor can still open the files. Conversely, disabling a link does not remove a team member's direct access.
What to do
When a project closes, inspect the folder's member list and each active view or edit link. Remove obsolete members and links separately. Test from an account that does not have owner or inherited access. Record whether the collaborator should retain an offline copy.
The distinction that matters
A link is a sharing mechanism, not proof that the recipient is an invited member; a member may not need the link at all. Removing your own access to a link does not switch the link off for everyone. If permission comes from a parent or team, contact its owner. Neither route can recall files a person downloaded earlier.
Dropbox shared links Dropbox shared-folder removal