Here is packages mapped to jar files.
Objects in the com.esri.arcgis.* package are java proxies which use an interop layer to communicate with core arcobject components. These can be used in two contexts – Engine usage or Server usage. These objects comprise a STATEFUL API.
Objects in the com.esri.adf.web.* package are the Web ADF components that provide a framework for building web applications based on the JSF standard. These web adf components internally leverage both the stateful and stateless APIs described above to communicate with ArcGIS Server.
+–arcgis_webcontrols.jar (generic foundation)
+–arcgis_webcontrols_ags.jar (specific to ArcGIS Server resource);
+–arcgis_webcontrols_arcims.jar (specific to ArcIMS resource);
+–arcgis_webcontrols_arcweb.jar (specific to ArcWeb resource);
+–arcgis_webcontrols_wms.jar (specifc to WMS resource);
Objects int he com.esri.arcgisws.* package are the stubs and service definitions for ArcGIS Server webservices based on the Axis toolkit. These objects comprise a STATELESS API.
Objects in the com.esri.adf.ejb.* package are the Enterprise ADF components that provide Geospatial EJBs. These components leverage the stateless API to communicate with ArcGIS Server.