The Shared Service Provider setting establishes the database in which the Ontolica Web parts on the same page will search. If your SharePoint farm includes more than one Shared Service Provider, then select the provider whose database you want to search from the drop-down list here.
Note that if you have added one or more shared service providers to SharePoint since you activated Ontolica, then the newer providers might not be shown on the list. To add them, deactivate and then reactivate Ontolica at the farm level (none of your Ontolica settings or Search-Center pages will be affected by this). See “Activating and Deactivating Farm-Level Features” for instructions.