The blacklist hides creators from all your future searches. You add a creator via the blacklist action in the tools menu of a search-result row (or on the profile). From then on, that account no longer appears in any of your search results — useful for creators you have already reviewed and rejected.
The blacklist is shared across your organization: a blocked creator is hidden from the search results of everyone in your account, and any team member can remove the entry again. You can review and manage your blacklist like a collection — open the blacklist via "Show Blacklist" in the collections area — and remove entries at any time to make the creators visible again.