ST_Geometry is a user-defined data type that allows you to store spatial data directly in a field in the table. The ST_Geometry type can be used with ArcGIS clients, plus it provides SQL access to simple feature class geometry.
You can add the ST_Geometry spatial data type to an existing PostgreSQL or Oracle database using the Create Spatial Type geoprocessing tool or Python script.
When you add the ST_Geometry type to an Oracle or PostgreSQL database, an sde user and storage space are created, as are system tables, views, functions, triggers, and other metadata objects to maintain ST_Geometry.
You can add the ST_Geometry spatial data type to an existing SQLite database using the CreateOGCTables SQL function. Alternatively, you can use the CreateSQLiteDatabase ArcPy function to create an SQLite database that uses the ST_Geometry spatial data type. See Spatially enable an SQLite database for more information.
When you add the ST_Geometry type to an SQLite database, ST_Geometry system tables are added to the database to maintain ST_Geometry metadata. The ST_Geometry SQL functions are stored in libraries that are external to the database.
For information on the ST_Geometry type and functions, see the Use ST_Geometry with SQL section of the ArcGIS help.