Administration Tool - Result Clustering Menu
Example: For the query CES AND Help, result clustering is likely to regroup search interface help documents in one cluster, Administration Tool help documents in another, etc. Whereas, ranking without result clustering displays those documents by relevance score only (ex.: two search interface documents can be separated by an Administration Tool and an Interface Editor one).
By default, result clustering is disabled. You can enable and configure results clustering (see Enabling and Customizing Result Clustering).