Levels within the range associated with the design of a database to store information in memory that stored by any means. External users (external level) you can use the database quickly.
Internal level is a level that is associated with the design of the database, data is stored in memory that stores either way. External users (External Level) will be able to use the database quickly.
Within a level related to the design of the database in the data storage memory that is stored in any external user level (External Level) then you will be able to use database quickly.