I said earlier that a GIS was the marriage between a (geo)graphical database and an attribute database. The geodatabase still adheres to this in concept. I also said that usually the attribute database was housed in a commercial relational database management system (RDBMS) as mentioned earlier. The new wrinkle is that the entire thing—geographic part and attribute part—is housed in a single RDBMS file. This means, from the point of view of the software, all of the geographic datasets have been rolled up with the attribute data into a single file. For ArcSDE databases this file may be located in one of several commercial relational database systems. To determine which commercial RDBMSs are used by Esri software, consult the help files for the version you are using.
Personal geodatabases are housed using the Microsoft Access database system. With ArcGIS 10. Differences between file or personal geodatabases and Esri’s more extensive products include the lack of ability to automatically keep up with versions of the data and restrictions of who can make changes to the database. Also, single user geodatabases are usually smaller and are run on less powerful machines.
With the single-file implementation of a GIS in a geodatabase, there is, therefore, no temptation to go in with the operating system to move, delete, or rename things; the components are somewhat hidden from the user, except through ArcCatalog and ArcMap.