External tables are defined as tables that do not reside in the database, and can be in any format for which an access driver is provided. Oracle Database provides two access drivers: ORACLE_LOADER and ORACLE_DATAPUMP. By providing the database with metadata describing an external table, the database is able to expose the data in the external table as if it were data residing in a regular database table.
An external table load creates an external table for data that is contained in an external data file. The load executes INSERT statements to insert the data from the data file into the target table.
The advantages of using external table loads over conventional path and direct path loads are as follows:
If a data file is big enough, then an external table load attempts to load that file in parallel.
An external table load allows modification of the data being loaded by using SQL functions and PL/SQL functions as part of the INSERT statement that is used to create the external table.
Oracle Database Administrator's Guide for information about creating and managing external tables