SQL: Structured Query Language - Oracle 10g Database Administration Concepts and Implementation Made Simple - page 68

Figure 2-20: Security management: Managing users, privileges and
roles. Users can be authenticated by the database or the OS. Privileges
can be assigned to users and roles.
Example:
CREATE USER asim
IDENTIFIED BY evergreen
DEFAULT TABLESPACE user_demo;
This statement will create a new user with the login as asim and
password as evergreen and whatever objects (tables, views etc.)
that user asim will create will reside in the user_demo
tablespace. Such types of accounts are called “Database-
Authenticated User Accounts ” where users get verified by the
database. There is another form of authentication which is called
“Externally Authenticated User Accounts ” or also known as
OPS$ accounts. Such users get verified by OS once they log in.
When Oracle 6 was introduced such category of accounts were