On an Oracle 12c database, login as sys as sysdba.
Create two users:
create user James identified by James;Now grant Ben the ability to connect through to James:
create user Ben identified by Ben;
grant create session to James;
grant create session to Ben;
alter user James grant connect through Ben;Now you are able to connect as Ben without knowing his password.
show userSo you can see that even though we are logging in as Ben, using the  brackets we are actually logging in as James;
USER is "JAMES"