The core toolboxes contain a mixture of tools available with specific license levels. These are shown in the tables on the linked ArcGIS Desktop Help Online page. An 'x' shows that the tool is available for that license level.
See the link in the Related Information section below for the ArcGIS Desktop Help Online topic, Licensing for geoprocessing tools.
The Coverage toolbox is only available with an ArcInfo license. All tools provided with extensions are available at any license level.