Geodatabase is short for 'geographic database.' Simply put, a geodatabase is a modern container for GIS data. It is a next-generation, object-relational geographic data model.
A geodatabase is conceptually similar to the familiar file-based coverage and shapefile data models but extends these models in some important ways. These include support for advanced geometry, continuous non-tiled data storage, user-defined relationships among features classes, and efficient storage of raster data.