What is the geodatabase?
The geodatabase is a collection of geographic datasets of various types used in ArcGIS and managed in either a file folder or a relational database. It is the native data source for ArcGIS and is used for editing and data automation in ArcGIS.
To learn more about the geodatabase, see Essential readings about the geodatabase in the ArcGIS help.
Learn more about What's new for geodatabases in ArcGIS 9.3? or What's new for geodatabases in ArcGIS 9.3.1?